I am a mathematician, so I use \cdot instead of \times

tex/header/stdmath.sty

@@ -74,7 +74,8 @@
 \RequirePackage{amsthm}                   % for theorems environments
 \RequirePackage{enumerate}                  % for different kind of numbering in enumerations
 \RequirePackage[version=4]{mhchem}  % chemical formulars. Provides \ce
-\RequirePackage[per-mode=fraction]{siunitx}  % provides nice typesetting for units and numbers
+\RequirePackage[per-mode=fraction,
+exponent-product=\cdot]{siunitx}  % provides nice typesetting for units and numbers
 
 % bibliography
 \newcommand{\bibfile}{.maindir/tex/bibliography.bib}