Giant magnetoelastic interaction in UFe2

Using the unique coverage of (Q, ω) space available on the BRISP spectrometer, we have investigated the low Q dynamical response of a single crystal of UFe2. A strong inelastic signal was found with a dispersion corresponding to the transverse acoustic phonon branch, forbidden in the first Brillouin zone. A detailed analysis of the neutron intensities as a function of temperature reveals a possible magnetic contribution superposed to this signal, which could originate from the magnon-phonon interaction, explaining the anomalous magnetoelastic behavior in this compound.