I am looking to get bold math symbols beyond simple characters. In particular, I'm having trouble with the following:

\bm{$a\xleftarrow{r} b$}

I've tried using several other packages besides bm, but all of them seem to yield the same

! Improper alphabetic constant

error. Are there any packages that can handle these types of math constructs? Or is there something simple I can add to the preamble to deal with this issue? Thanks!

  • 1
    \bm should be used inside the math. Jan 28, 2016 at 14:02

1 Answer 1


As described in the documentation of bm in 3.5 Strange failures you sometimes need to add braces to protect complicated commands. But in your case I would simply use \mathversion{bold}






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