Here is the MWE. Once I added [xindy] while calling imakeidx, the sorting is fixed. But now xindy puts letter headings to each group. How can I get rid of those?

\documentclass{memoir}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\usepackage[citestyle=authoryear-comp,bibstyle=authoryear,hyperref=true,maxcitenames=3,doi=false,url=true,backend=biber,natbib=true,maxbibnames=99,uniquename=false,uniquelist=false,indexing=cite]{biblatex}

\usepackage[xindy]{imakeidx}

\makeindex
\usepackage[itemlayout=abshang,indentunit=10pt]{idxlayout}

\usepackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@article{auth00a,
author = {Author},
title = {MyBook A},
date = {2000}
}
@article{auth00b,
author = {Author},
title = {MyBook B},
date = {2000}
}

@article{morris2008effective,
Author =       {Morris, Saul S. and Cogill, Bruce and Uauy, Ricardo},
Journal =      {The Lancet},
Number =       9612,
Pages =        {608--21},
Title =        {Effective international action against
undernutrition: Why has it proven so difficult and
what can be done to accelerate progress?},
Volume =       371,
Year =         2008
}

@article{biberanak2002,
Author =       {Biber, F. Z{\"u}mr{\"u}t and {\"U}nak, Perihan and
Yurt, Fatma},
sortname =    {Biber, F. Zumrut and Unak, Perihan and Yurt, Fatma},
Doi =          {10.1080/10256010208033316},
Journal =      {Isotopes in Environmental and Health Studies},
Number =       2,
Pages =        {87--93},
Title =        {Stability of iodine content in iodized salt},
Volume =       38,
Year =         2002,
Bdsk-Url-1 =   {dx.doi.org/10.1080/10256010208033316}
}

@article{wang2014trends,
Author =       {Wang, Dong D. and Leung, Cindy W. and Li, Yanping and
Ding, Eric L. and Chiuve, Stephanie E. and Hu, Frank B.
and Willett, Walter C.},
Journal =      {JAMA Internal Medicine},
Number =       10,
Pages =        {1587--95},
Timestamp =    {2015.02.27},
Title =        {Trends in dietary quality among adults in the
{U}nited {S}tates: 1999 through 2010},
Volume =       174,
Year =         2014
}

\end{filecontents*}

\begin{document}
\parencite{auth00a,auth00b,wang2014trends,morris2008effective,biberanak2002}

\printindex

\end{document}


I use following command to compile:

xelatex -interaction nonstopmode mwebib
biber mwebib
xelatex -interaction nonstopmode mwebib
xindy -M texindy -M page-ranges -L Turkish -C utf8 mwebib.idx
xelatex -interaction nonstopmode mwebib
xelatex -interaction nonstopmode mwebib


Here is an image of what I get

It would be better if {\"U}nak was sorted as Unak, and no headings were given to letter groups in the bibliography.

Here is the log of xindy run:

Opening logfile "/dev/null" (done)
Finalizing indexstyle... (done)

Processing index... [10%] [20%] [30%] [40%] [50%] [60%] [70%] [80%] [90%] [100%]
Finished processing index.

Writing markup... [10%] [20%] [30%] [40%] [50%] [60%] [70%] [80%] [90%] [100%]
Markup written into file "./mwebib.ind".

• There is no difference in output between citestyle=authoryear-comp, bibstyle=authoryear and style=authoryear-comp. But the latter is arguably easier on the eyes in the source code. There is no need for hyperref=true, the default auto option will turn on hyperref support automatically, if the hyperref is loaded. – moewe Sep 1 '15 at 6:58
• Can you please add a full MWE of what your index looks like and how it is created? Because from what I can see, the sorting in the bibliography should be just fine. – moewe Sep 1 '15 at 7:00
• Note that the sorting in the index is not done by biblatex, but your favourite index tool (makeindex, xindy). So that tool needs to support proper UTF8 sorting (I think xindy should be able to do that, I'm not sure about makeindex). – moewe Sep 1 '15 at 9:40
• The sorting is right on my machine. Is your system up to date? Does \newcommand*\lettergroup[1]{} seem to do the trick with the groups? Otherwise you will have to change the .xdy file as in Customize xindy index layout. – moewe Sep 2 '15 at 7:18
• I have re-tagged the question as it is not really about biblatex, but rather about xindy now. – moewe Sep 2 '15 at 7:23

As other people said, I get the right grouping for U and Ü with my MacTeX2015. In order to remove headings you have only to redefine the \lettergroup command inside the style file. In this case you can decide that \lettergroup is only a \par command.

% arara: xelatex
% arara: biber
% arara: xelatex: {shell : yes}
% arara: xelatex
\documentclass{memoir}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\usepackage[citestyle=authoryear-comp,bibstyle=authoryear,hyperref=true,maxcitenames=3,doi=false,url=true,backend=biber,natbib=true,maxbibnames=99,uniquename=false,uniquelist=false,indexing=cite]{biblatex}

\usepackage{imakeidx}

\makeindex[program=xindy,options= -C utf8 -M indexstyle]
\usepackage[itemlayout=abshang,indentunit=10pt]{idxlayout}

\usepackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@article{auth00a,
author = {Author},
title = {MyBook A},
date = {2000}
}
@article{auth00b,
author = {Author},
title = {MyBook B},
date = {2000}
}

@article{morris2008effective,
Author =       {Morris, Saul S. and Cogill, Bruce and Uauy, Ricardo},
Journal =      {The Lancet},
Number =       9612,
Pages =        {608--21},
Title =        {Effective international action against
undernutrition: Why has it proven so difficult and
what can be done to accelerate progress?},
Volume =       371,
Year =         2008
}

@article{biberanak2002,
Author =       {Biber, F. Z{\"u}mr{\"u}t and {\"U}nak, Perihan and
Yurt, Fatma},
sortname =    {Biber, F. Zumrut and Unak, Perihan and Yurt, Fatma},
Doi =          {10.1080/10256010208033316},
Journal =      {Isotopes in Environmental and Health Studies},
Number =       2,
Pages =        {87--93},
Title =        {Stability of iodine content in iodized salt},
Volume =       38,
Year =         2002,
Bdsk-Url-1 =   {dx.doi.org/10.1080/10256010208033316}
}

@article{wang2014trends,
Author =       {Wang, Dong D. and Leung, Cindy W. and Li, Yanping and
Ding, Eric L. and Chiuve, Stephanie E. and Hu, Frank B.
and Willett, Walter C.},
Journal =      {JAMA Internal Medicine},
Number =       10,
Pages =        {1587--95},
Timestamp =    {2015.02.27},
Title =        {Trends in dietary quality among adults in the
{U}nited {S}tates: 1999 through 2010},
Volume =       174,
Year =         2014
}
\end{filecontents*}
\begin{filecontents*}{indexstyle.xdy}
(markup-index :open  "\begin{theindex}~n
\providecommand*\lettergroupDefault[1]{}
\providecommand*\lettergroup[1]{%
\par}"
:close "~n~n\end{theindex}~n"
:tree)

(markup-locclass-list :open "\dotfill " :sep ", ")

;; delim_n <string>         ", "

(markup-locref-list   :sep ", ")

;; delim_r <string>         "--"

(markup-range :sep "--")

;; Local Variables:
;; mode: lisp
;; End:
\end{filecontents*}

\begin{document}
\parencite{auth00a,auth00b,wang2014trends,morris2008effective,biberanak2002}

\printindex

\end{document}


the output is:

• Do you get two groups for U and Ü, or just one? I get two but want one. Could you please add an image of your output. This is very peculiar. – len71 Sep 2 '15 at 23:50
• It is probably just a matter of (sort-rule "ü" "u")? I couldn't get (sort-rule "ü" "a") going here, but I'm not sure how to use it. – moewe Sep 3 '15 at 6:50
• In this case there is no problem if you use \newcommand, because \lettergroup is not already defined. xindy has a lot of option, you can build lettergroups as you want, for example you can create A-C, D-F,... groups. You can chhose that the X letter shall be indexed beteween M and N. It's really powerful, if you know how to use it :-) – Francesco Endrici Sep 3 '15 at 6:52
• I thought as much. That little trick would save us having to create a .xdy for this. Do you think you can give an example of this sort/merging maybe using some crazy example? That might help the OP to override a shoddy default if that is the problem here. – moewe Sep 3 '15 at 6:54