stix2 FONT: bold greek

Question

I installed STIX2 fonts in otf format on my Win10 machine.

I tried:

---

\documentclass{minimal}
\usepackage{bm}
\usepackage{fontspec}
\usepackage{unicode-math}
\setmainfont{STIX2Text-Regular.otf}
\setmathfont{STIX2Math.otf}
\begin{document}
$$
\bm{\alpha}
$$
\end{document}

--------------------------------

by (under xelatex, miktex 2.9) I get error:

! Improper alphabetic constant.
<to be read again> 
               \mitalpha 
l.11  \bm{\alpha}
             ? 
Process has been terminated ...

------------------------

I can get standard text to work but I have issues with math. Where could I learn about this? I can use STIX rel.1x fonts in standard latex compilation (with \usepackage{stix}) but I wanted to try STIX2 for which there is no latex package yet.

Thanks Maurizio

Answer 1

The bm-package and unicode-math (often/sometimes) doesn't work well together. See e.g. https://tex.stackexchange.com/a/315389/2388

You can use \symbf to get a bold alpha:

\documentclass{article}
\usepackage{bm}
\usepackage{fontspec}
\usepackage{unicode-math}

\setmainfont{STIX2Text-Regular.otf}
\setmathfont{STIX2Math.otf}
\begin{document}

$\alpha\symbf{\alpha}$

\end{document}