  We reconsider the recent observation by the D0 experiment of a sizable
like-sign dimuon charge asymmetry, highlighting that it could be affected by
CP-violating New Physics contributions not only in Bd- and Bs-meson mixings,
but also in semileptonic decays of b and c quarks producing muons. The D0,
measurement could be reconciled with the Standard Model expectations for
neutral-meson mixings, provided that the CP asymmetry in semileptonic b (c)
decays reaches 0.3 % (1%). Such effects, which lie within the available (rather
loose) experimental bounds, would be clear indications of New Physics and
should be investigated experimentally.
