Pseudogap due to coherence Kondo effect in CeNiSn and CeRhSb

Specific heat of single crystal of CeNiSn has been measured between 1.3 and 60 K and analyzed together with that of polycrystals of CeRhSb, CeNi1-xPtxSn (x = 0.03, 0.06, 0.12 and 0.20) and CeNi1-yCoySn (y = 0.03 and 0.10). The magnetic specific heat divided by temperature C-m/T of CeNiSn and CeRhSb exhibits a maximum and substantially decreases at low temperatures indicating the energy gap opening in the heavy quasiparticle band. The Kondo temperatures T-K were estimated to be 51 K for CeNiSn and 89 K for CeRhSb by fitting the magnetic entropy S-m. rising the reduced temperature (T) over tilde = T/T-K, C-m/T was plotted in C-m/(T) over tilde versus (T) over tilde. The plot reveals the obvious relation between the energy gap formation and the Kondo effect.