Phonon spectrum of the ferromagnetic superconductorUGe2and consequences for its specific heat

We report inelastic neutron scattering measurements of the phonon spectrum of the pressure-induced ferromagnetic superconductor ${\mathrm{UGe}}_{2}$. The phonon contribution to the specific heat was estimated from a fit to our data. The excess specific heat previously noted at around ${T}_{x}\ensuremath{\approx}\phantom{\rule{0.3em}{0ex}}30\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ is not due to phonons but is well described by the temperature dependence of the magnetic order parameter at the molecular field level.