Coherent neutrino magnetic conversion in crystals

We study coherent enhancement of neutrino electro-magnetic conversion in crystals. Large coherence length which grows with the neutrino energy makes the coherent enhancement particularly effective for very small masses. We derive constraints on the conversion rate which follow from the Fresnel effects in scattering of neutrinos on atomic chains. We comment on possible applications of the crystal converter to searches for non-diagonal neutrino magnetic transitions in the CERN neutrino beam and on future muon colliders.