Accents package incompatible with bm?

Reading egreg's answer to Decrease length of underline in math, I wanted to use the accents package for lower bars in math mode.

It seem however that the package is incompatible with the bm package. When I add \usepackage{accents} to my preamble, even without using any commands related to the package, I get error messages for all my uses of \bm.

Missing number, treated as zero ...s when only one specific $\bm{\tilde{a}} Missing control sequence inserted ...s when only one specific$\bm{\tilde{a}}

Missing } inserted ...s when only one specific $\bm{\tilde{a}} Missing } inserted ...s when only one specific$\bm{\tilde{a}}

Missing } inserted ...s when only one specific $\bm{\tilde{a}} Missing } inserted ...s when only one specific$\bm{\tilde{a}}

Extra }, or forgotten \endgroup ...s when only one specific $\bm{\tilde{a}} Missing control sequence inserted ...s when only one specific$\bm{\tilde{a}}

Parameters must be numbered consecutively ...s when only one specific $\bm{\tilde{a}} Missing number, treated as zero ... \leq \left| \sum_{a_i \in \bm{\tilde{a}} Missing control sequence inserted ... \leq \left| \sum_{a_i \in \bm{\tilde{a}} Missing } inserted ... \leq \left| \sum_{a_i \in \bm{\tilde{a}} Extra }, or forgotten \endgroup ... \leq \left| \sum_{a_i \in \bm{\tilde{a}} Missing control sequence inserted ... \leq \left| \sum_{a_i \in \bm{\tilde{a}} Parameters must be numbered consecutively ... \leq \left| \sum_{a_i \in \bm{\tilde{a}} Missing number, treated as zero for any$\bm{\tilde{a}}

Missing control sequence inserted for any $\bm{\tilde{a}} Missing } inserted for any$\bm{\tilde{a}}

Extra }, or forgotten \endgroup for any $\bm{\tilde{a}} Missing control sequence inserted for any$\bm{\tilde{a}}

Parameters must be numbered consecutively for any $\bm{\tilde{a}} Missing number, treated as zero ...he case in particular for$\bm{\tilde{a}}

Missing control sequence inserted ...he case in particular for $\bm{\tilde{a}} Missing } inserted ...he case in particular for$\bm{\tilde{a}}

Extra }, or forgotten \endgroup ...he case in particular for $\bm{\tilde{a}} Missing control sequence inserted ...he case in particular for$\bm{\tilde{a}}

Parameters must be numbered consecutively ...he case in particular for $\bm{\tilde{a}}  Is there a way to make both packages compatible? - Minimal example please – daleif Jul 5 '13 at 11:07 1 Answer Instead of $\bm{\tilde{a}}$, use $\tilde{\bm{a}}$. OR Use $\bm{{\tilde{a}}}\$, an extra grouping inside \bm{{...}}.

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Great, I tried the first solution you proposed and it works! Could you add a word of explanation about why the order or extra grouping matters? –  Martin Van der Linden Jul 5 '13 at 11:11
I think: \bm command will expand its argument and spilt everything inside it, causing the error. The grouping here will remove the error. –  Jagath AR Jul 5 '13 at 11:46