Biblatex reference sorting in same-first author, different-year entries

Question

I'm using the biblatex bibliography package and I need the references to be sorted first by name, and references with the same first author to be sorted then by ascending year. In my preamble, the biblatex package is set like this:

\documentclass{book}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage[autostyle=true]{csquotes}

\usepackage[backend=biber,style=authoryear,natbib=true,sorting=nyt]{biblatex}

\addbibresource{library.bib}

\begin{document}

Text \citep{Jinek2012}, and more text \citep{Jinek2013}.

\printbibliography[title=References]

\end{document}

While it may follow the nyt sorting scheme in some cases, it's overriden in others. In my library.bib, two of the problematic entries look like this:

@article{Jinek2013,
author = {Jinek, M. and Cheng, A. and Lin, S. and Ma, E. and Doudna, J. and 
East, A.},
journal = {eLIFE},
title = {{RNA-programmed genome editing in human cells}},
volume = {2},
year = {2013}
}

@article{Jinek2012,
author = {Jinek, M. and Chylinski, K. and Fonfara, I. and Hauer, M. and 
Doudna, J. and Charpentier, E.},
number = {6096},
pages = {816--821},
title = {{A programmable dual-RNA-guided DNA endonuclease in adaptive 
bacterial immunity}},
volume = {337},
year = {2012}
}

Yet the result is:

However, this problem does not seem to apply for all same-first author, different-year articles, like these ones:

Is there any way I could force all same-first author, different-year articles to be sorted ascendingly by year after author sorting?

Thanks in advance

Answer 1

biblatex sorts by all authors and not just the first and so the sorting is expected.

You can restrict sorting to the first author by extracting it with RegExp and writing it to sortname.

\documentclass[british]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{csquotes}

\usepackage[style=authoryear, backend=biber]{biblatex}

%\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@article{Jinek2013,
author = {Jinek, M. and Cheng, A. and Lin, S. and Ma, E. and Doudna, J. and 
East, A.},
doi = {10.7554/eLife.00471.001},
journal = {eLIFE},
title = {{RNA-programmed genome editing in human cells}},
url = 
{https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3557905/pdf/elife00471.pdf 
http://elife.elifesciences.org/content/2/e00471},
volume = {2},
year = {2013}
}
@article{Jinek2012,
author = {Jinek, M. and Chylinski, K. and Fonfara, I. and Hauer, M. and 
Doudna, J. and Charpentier, E.},
doi = {10.1126/science.1225829},
isbn = {6212011575},
issn = {10959203},
journal = {Science},
number = {6096},
pages = {816--821},
title = {{A programmable dual-RNA-guided DNA endonuclease in adaptive 
bacterial immunity}},
volume = {337},
year = {2012}
}
\end{filecontents}

\addbibresource{\jobname.bib}
\addbibresource{biblatex-examples.bib}

\DeclareSourcemap{
  \maps[datatype=bibtex]{
    \map{
      \step[fieldsource=author, match=\regexp{(.*?)\s+and\s+}]
      \step[fieldset=sortname, fieldvalue={$1}]
    }
  }
}

\begin{document}
\cite{sigfridsson,Jinek2013,Jinek2012}
\printbibliography
\end{document}