I noticed a strange citation key in my document. All citation keys with multiple authors are generated like this for example: `[Ber+07]`
Where does this `+` sign come from? I setup biblatex like so:

``````\usepackage[
backend=biber,
maxcitenames=3,
maxbibnames=3,
style=alphabetic,
sorting=nyt]{biblatex}
\DefineBibliographyStrings{ngerman}{
}
``````

Do I have to write my own biblatex style?

• `maxcitenames=3` has little effect with `style=alphabetic,` and is the default value anyway. `maxbibnames=3` is also the default. (Indeed `maxnames=3` is the default setting, which sets both of the mentioned values to 3.) `sorting=nyt` is unusual together with `style=alphabetic`, the standard for `alphabetic` is `sorting=anyt`, which sorts by label first. – moewe Dec 20 '17 at 15:36
• – moewe Dec 20 '17 at 15:46

The "+" is just a signal that the list of authors/editors has been truncated to fit into `maxalphanames` (the default value is 3), it works just like "et al." (and `maxcitenames`) in other styles.

Uthor et al. 2006; Uthor and Riter 2006

would be

Uth+06; UR06

The exact symbol is controlled with `\labelalphaothers`, so you could say

``````\renewcommand*{\labelalphaothers}{\&al}
``````

to get

Uth&al06

You can increase `maxalphanames` to a higher value if you don't want your list truncated.