Thermal expansion and magnetostriction in CeRh<SUB>2</SUB>Si<SUB>2</SUB> under high pressure

Thermal expansion coefficients of polycrystalline CeRh2Si2 under high pressure up to 2.15GPa have been measured in the temperature range from 5 to 300K. It is found that the antiferromagnetic ordering temperature TN1 and the magnetic order-order transition temperature TN2 decrease with increasing pressure and the antiferromagnetism disappears at high pressure. A positive spontaneous magnetostriction, of the order of 10-4, is observed below TN1, which also disappears above Pc=1.11GPa. The results are explained qualitatively by the competition between the Kondo and the RKKY interactions. Similarity between the present P-T phase diagram and the Doniach's one is pointed out