  We study the nuclear mu-e conversion in the general framework of the
effective Lagrangian approach without referring to any specific realization of
the physics beyond the standard model (SM) responsible for lepton flavor
violation (LFV). We analyze the role of scalar meson exchange between the
lepton and nucleon currents and show its relevance for the coherent channel of
mu-e conversion. We show that this mechanism introduces modifications in the
predicted mu-e conversion rates in comparison with the conventional direct
nucleon mechanism, based on the contact type interactions of the nucleon
currents with the LFV leptonic current. We derive from the experimental data
lower limits on the mass scales of the generic LFV lepton-quark contact terms
and demonstrate that they are more stringent than the similar limits existing
in the literature.
