We have measured the specific heat and magnetocaloric effect of URu₂Si₂ at magnetic fields up to 45 T. The large specific heat anomaly at T₀(H = 0) = 17 K shifts to lower temperatures when the magnetic field is increased and is suppressed at 36 T. Between 36 T and 38 T a new anomaly in the specific heat  versus  temperature indicates a magnetic phase never previously reported. At H \geq 40 T no transition is observed and crystal electric field effects dominate the specific heat. Measurements of the magnetocaloric effect are used to stablish a new phase diagram for URu₂Si₂.

PACS numbers: 71.27.+a, 75.30.Kz, 75.30.Sg, 71.10.Hf