[lltx] unicode-math + mathtools

[Arno Trautmann]

Hi all,

the following document fails because unicode-math overwrites the 
definition of mathtools:

\documentclass{minimal}

\usepackage{mathtools}
\usepackage{unicode-math}
\setmathfont{XITS-math}

\begin{document}
\[\underbracket{abc}\]
\[\underbracket[7pt]{abc}\]
\end{document}

\underbracket works, but the optional arguments are gone. I tried to use 
\let to restore the definition of mathtools after loading unicode-math, 
but did not succeed. Is this fixable or incompatible in principle?

cheers
Arno