Thermal Variation of Ce Valence in Mixed Valence-Kondo Lattice Systems CeT2(Si1-xGex)2 with T= Mn and Ni

The results on the thermal variation of Ce L3-valence in CeT2(Si1-xGex)2 series with 0(le)x(le)1 and T=Mn and Ni are reported. It is observed that for both series, the Ce valence increases with decreasing temperature and has little thermal variation for samples in the nearly trivalent regime. The magnitude of this thermal variation in the T=Mn series is much greater than in the T=Ni series. The results are explained by the degenerate Anderson model and correlated with the specific heat data.