LOW-TEMPERATURE PROPERTIES OF THE HEAVY-FERMION COMPOUND CERU2SI2 AT THE METAMAGNETIC TRANSITION

Magnetization measurements performed below 1 K on a single-crystalline sample of the heavy fermion compound CeRu2Si2 are reported. The field variation of the linear term of the specific heat gamma derived from these data (via a Maxwell relation) exhibits a large peak at the metamagnetic-like transition at B* ( = 7.7 at T --> 0). Thermal-expansion measurements, show a drastic drop of the temperature where a Fermi liquid behavior is reached when B --> B*. Similar experiments performed on a single-crystalline Ce0.95La0.05Ru2Si2 sample show a broadening of all the anomalies at B* and a reduction of their intensities. These results strongly suggest that pure CeRu2Si2 approaches a magnetic instability at B* for T --> 0.