SPECIFIC-HEAT OF HEAVY-FERMION URU2SI2 IN HIGH MAGNETIC-FIELDS

We have performed specific-heat measurements on the heavy-fermion supe rconductor URu2Si2, in magnetic fields up to 17.5 T. A sharp peak in t he specific heat signals the antiferromagnetic transition at T-N=17.5 K, which shifts to lower temperatures in applied magnetic fields. In o rder to describe the specific heat below T-N, we have used the charact eristic features of the excitation spectrum measured by neutron scatte ring. The relative field dependence of the antiferromagnetic transitio n 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.