Sorting author index made using biblatex, removing letter group headings

Question

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*}
\addbibresource{\jobname.bib}

\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)
Reading indexstyle...
Loading module "/var/folders/hj/hqfjch716qg5php160jbtfgh0000gn/T/z2uZtkJFip"...
Loading module "lang/Turkish/utf8-lang.xdy"...
Loading module "lang/turkish/utf8.xdy"...
Finished loading module "lang/turkish/utf8.xdy".
Finished loading module "lang/Turkish/utf8-lang.xdy".
Loading module "texindy.xdy"...
Loading module "numeric-sort.xdy"...
Finished loading module "numeric-sort.xdy".
Loading module "latex.xdy"...
Loading module "tex.xdy"...
Finished loading module "tex.xdy".
Finished loading module "latex.xdy".
Loading module "latex-loc-fmts.xdy"...
Finished loading module "latex-loc-fmts.xdy".
Loading module "makeindex.xdy"...
Finished loading module "makeindex.xdy".
Loading module "latin-lettergroups.xdy"...
Finished loading module "latin-lettergroups.xdy".
Finished loading module "texindy.xdy".
Loading module "page-ranges.xdy"...
Finished loading module "page-ranges.xdy".
Finished loading module "/var/folders/hj/hqfjch716qg5php160jbtfgh0000gn/T/z2uZtkJFip".
Finished reading indexstyle.
Finalizing indexstyle... (done)

Reading raw-index "/var/folders/hj/hqfjch716qg5php160jbtfgh0000gn/T/tD8Zga0_Dw"...
Finished reading raw-index.

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".

Answer 1

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*}
\addbibresource{\jobname.bib}

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

\printindex

\end{document}

the output is: