Possibility of a first-order transition in the magnetization study of the anomalous superconducting mixed state of CeRu<SUB>2</SUB>

All qualitative features of the superconducting mixed state behaviour of a 5% Nd-doped CeRu2 sample studied earlier, [Physica C 279 (1997) 70] are reproduced in undoped samples of CeRu2. This establishes the fact that the observed behaviour is a characteristic of the CeRu2 family. We also present new results of polycrystalline CeRu2 that are consistent with the existence of a first-order phase transition described by the Clausius-Clapeyron relation