I'm using biblatex with the alphabetic style.
If there are multiple authors it takes the first Letter of every author (first example), but I'd like to have just the first author (second example, but also if there would be multiple authors) - how can I achieve this? I was not able to find the according option in biblatex.

Though there would be a doubling, both notations in the square brackets should be the same in this case.
other example:

should be [Box60] and [Box51].
My minimal example:
\documentclass{article}
\usepackage[backend=bibtex,style=alphabetic]{biblatex}
\begin{filecontents}{references.bib}
@ARTICLE{boxwilson,
author={Box, G. E. P. and Wilson, K. B. },
journal={Journal of the Royal Statistical Society. Series B (Methodological)},
title={On the Experimental Attainment of Optimum Conditions},
year={1951},
volume={13},
number={1},
pages={1-45},
,}
}
\end{filecontents}
\bibliography{references.bib}
\begin{document}
\cite{boxwilson}
\printbibliography
\end{document}
A distinction between doubled entries is alright: [Box60a] and [Box60b].
Thank you!
Edit:

\DeclareLabelalphaTemplate. I can't test a solution as you didn't provide a minimal example so you will have to find out the exact code yourself. – Ulrike Fischer Jul 29 '14 at 11:45biberinstead ofbibtex. That's necessary for the\DeclareLabelalphaTemplate-part. – musicman Jul 29 '14 at 14:16.bibfile with Biber though? Assuming your.texfile is calledmwe.tex(the name of the.bibfile is irrelevant), you will have to runpdflatex mwe,biber mwe,pdflatex mwe,pdflatex mwe. Are you sure you have Biber installed? What happens if you typebiberin the command line? – moewe Jul 29 '14 at 14:21