FIELD SUPPRESSION OF THE HEAVY-FERMION STATE IN CERU2SI2

Specific-heat measurements have been performed on a single-crystalline sample of the heavy-fermion compound CeRU2Si2 in strong magnetic fields up to 20 T along the tetragonal axis in the temperature interval 1. 5 < T < 30 K. The linear electronic term in the specific heat (gamma) passes through a pronounced maximum at a field B* congruent-to 7.8 T, where the metamagneticlike transition occurs. For fields above B*, the mass enhancement decreases gradually, resulting in a reduction of the effective mass at 20 T by approximately 80% with respect to the zero-field value. In the high-field region, the data have been analyzed using a simple single-resonance-level model.