THE HEAVY-FERMION COMPOUND CERU2SI2 - MAGNETIC INSTABILITY, LATTICE QUASICOLLAPSE AND METAMAGNETISM

The physical properties of the heavy fermion compound CeRu2Si2 are rev iewed. Since this compound is close to a magnetic instability, special attention is paid to its magnetization in which a metamagnetic-like t ransition occurs at a field H-M of 7.7 T and to the strong coupling be tween this effect and the volume, leading to a quasi-collapse of the l attice. It is shown that the value of the differential susceptibility at H-M reaches an intrinsic finite limit at very low temperature. Diff erent theoretical models are discussed.