\defaultfontfeatures{Ligatures=TeX}
\setmainfont[ItalicFont=FreeSerifbItalic.otf,
BoldFont=FreeSerifbBold.otf,
BoldItalicFont=FreeSerifbBoldItalic.otf,SmallCapsFont=FreeSerifb-SmallCapsAlt.otf]{FreeSerifb.otf}
%\setmathfont{XITSMath-Regular.otf}
\setmathfont{STIXTwoMath-Regular.otf}
\setmathfont[range=\mathup/{num,latin,Latin,greek,Greek}]{FreeSerifb.otf} 
\setmathfont[range=\mathbfup/{num,latin,Latin,greek,Greek}]{FreeSerifbBold.otf} 
\setmathfont[range=\mathit/{num,latin,Latin,greek,Greek}]{FreeSerifbItalic.otf} 
\setmathfont[range=\mathbfit/{num,latin,Latin,greek,Greek}]{FreeSerifbBoldItalic.otf}
\endinput