METAMAGNETISM AND LOW-TEMPERATURE PROPERTIES OF CE5SI3

Tetragonal Cr5B3-type Ce5Si3 shows a metamagnetic jump in the magnetiz ation curve around 40 kOe at 1.3 K. In order to clarify the mechanism, we performed specific heat, AC magnetic susceptibility and magnetizat ion measurements on polycrystalline Ce5Si3-delta (0 less than or equal to delta less than or equal to 1) and (Ce1-xLax)(5)Si3-delta (0 less than or equal to x less than or equal to 1) in magnetic fields up to 1 50 kOe and in temperatures down to 0.4 K. The magnetic properties were hardly affected with delta, but strongly affected with x. For x = 0.2 5, the metamagnetism disappeared completely. Anomalous low temperature behavior including the metamagnetism is discussed in connection with a Ce-dimer model with ground singlet and excited triplet states.