>I just want to keep the point in mind, that \mathsf is the prescribed
>font for tensors in mathematical formulae e. g. by the IUPAP (International
>Union of Pure and Applied Physicists) recommendations. And it is natural to
>name some tensors by greek letters (not necessarily confined to uppercase).
I find this interesting: Do they state a reason for this recommendation,
so that there is a general principle behind it, like the idea with
typesetting constant names upright?
(I picked an applied particle physics book at random, and it did not
typeset tensors sans serif.)