# How to have special characters (e.g. german umlauts) inside bibkeys?

I really like biblatex [backend=biber] to use with UTF8, as many citations I use will have some special characters esp. in the name field. This works totally great until I want to use e.g. german Umlauts (those strange characters: ü,ö,ä,ß) inside of the bibkey field. However I cannot get this to work:

\documentclass{article}
\usepackage{filecontents}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[backend=biber]{biblatex}

\begin{filecontents}{x.bib}
@article{Böttger2013,
title={Three-dimensional mean-shift edge bundling for the visualization of functional connectivity in the brain},
author={Böttger, Joachim and Schafer, Andreas and Lohmann, Gabriele and Villringer, Arno and Margulies, Daniel},
year={2013},
publisher={IEEE}
}
\end{filecontents}
\begin{document}
Foo bar \cite{Böttger2013}.
\printbibliography
\end{document}


I always get something like this:

Biber says in its first run:

WARN - I didn't find a database entry for 'B\IeC {\"o}ttger2013' (section 0)


leaving me with undefined references. Is there a way around? If not I think the easiest way is to use Boettger2013 instead of the UTF8 umlauts then.

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The citation key is just a label and Herr Böttger won't be aware you're not correctly spelling his name in the key. ;-) – egreg Oct 2 '13 at 21:21
biber supports this but pdftex might have problems. As @Nils mentions, if you use LuaTeX or XeTeX, it'll be ok. – PLK Oct 3 '13 at 9:17

Yes, it's best to avoid using UTF8 chars in bibkeys. Even with biber. The problem is with pdfLaTeX's creation of the .aux file (have a look at it). If you use LuaTeX or XeLaTeX, it'll be okay. Still, I suggest you stay away from those chars (only in bibkeys, of course).

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