Specific heat of heavy-fermion URu2Si2 in high magnetic fields

We have performed specific-heat measurements on the heavy-fermion superconductor URu2Si2, in magnetic fields up to 17.5 T. A sharp peak in the specific heat signals the antiferromagnetic transition at T-N=17.5 K, which shifts to lower temperatures in applied magnetic fields. In order to describe the specific heat below T-N, we have used the characteristic features of the excitation spectrum measured by neutron scattering. The relative field dependence of the antiferromagnetic transition temperature T-N and the energy gap Delta in the magnetic excitation spectrum can be described by a single scaling relation of the form [1-(B/B-0)(2)]. The scaling field of 48.5 T is close to the metamagnetic transition field B*=40 T, where the heavy-fermion state is suppressed.