# undefined control sequence \abx@aux@sortscheme

I am trying to start a basic tex document with bibtex citations as follows:

\documentclass{article}

\usepackage[backend=bibtex]{biblatex}
\bibliography{biblo}

\begin{document}
\printbibliography
\end{document}


However, when I run pdflatex mytexfile.tex I receive the error that \abx@aux@sortscheme is undefined. How can I resolve this?

• The syntax should be \addbibresource{biblo.bib}. Sep 9, 2016 at 22:01
• I think this error occurs after having changed some options to biblatex or removing the inclusion itself, then recompiling --> there is some code left in .aux file. Try to remove the aux-file
– user31729
Sep 9, 2016 at 22:04
• @Bernard: Yes, but \bibliography{biblo} still works (however not recommended)
– user31729
Sep 9, 2016 at 22:04
• @Christian Hupfer: That Biblatex is really a good lad… Sep 9, 2016 at 22:06
• @Bernard: On page 71 of current biblatex.pdf: \bibliography ... The legacy command... and as a marginnote: Deprecated (see at the bottom of the page)
– user31729
Sep 9, 2016 at 22:08

The reported error \abx@aux@sortscheme being undefined is a consequence of changing options to biblatex or having removed the \usepackage[...]{biblatex} entry followed by recompilation.
@aux indicates that this setting is written to the .aux file, after changing or removing this entry is still left in the .aux file and causes the error message during the next run.
Solution: Delete the .aux file and recompile.
A similar error occurs when changing language options from babel.
Side note: \bibliography is a deprecated command in conjunction with biblatex -- use \addbibresource instead.