Specific heat of heavy-fermionURu2Si2in high magnetic fields

We have performed specific-heat measurements on the heavy-fermion superconductor ${\mathrm{URu}}_2{\mathrm{Si}}_2$ in magnetic fields up to 17.5 T. A sharp peak in the specific heat signals the antiferromagnetic transition at $T_N=17.5\mathrm{}\mathrm{K},$ 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 Δ in the magnetic excitation spectrum can be described by a single scaling relation of the form $\left[1-{(B/B}_0{)}^2\right].$ The scaling field of 48.5 T is close to the metamagnetic transition field $B^{*}=40\mathrm{}\mathrm{T},$ where the heavy-fermion state is suppressed.