Coherent Kondo-lattice ground state in CeNi_0.85Rh_0.15Sn alloy

We have carried out structural, magnetic and transport measurements on CeNi_0.85T_0.15Sn (T=Ni, Ru, Rh and Pd) alloys in order to understand the complex low-temperature transport properties of the Kondo semiconductor CeNiSn. The resistivity measurements show that the observed low-temperature rise in the resistivity of CeNiSn becomes less pronounced with Ru and Pd substitution. Further, the resistivity of CeNi_0.85Rh_0.15Sn alloy shows the onset of the coherent Kondo-lattice ground state below 18 K and exhibits a T² behaviour below 7 K. The observed large negative magnetoresistance in CeNiSn at 1.7 K suggests that the energy gap decreases as the magnetic field increases. Positive magnetoresistance is observed in LaNiSn and CeNiSn at high temperatures and high fields. The negative magnetoresistance of CeNi_0.85T_0.15Sn (T=Rh and Pd) alloys exhibits a scaling behaviour as proposed by Schlottmann for single ion Kondo impurity. CeNi_0.85Rh_0.15Sn alloy exhibits positive magnetoresistance at 2 K and negative minimum magnetoresistance at 5 K, which further confirms the presence of a coherent Kondo-lattice ground state. The susceptibilities of all these alloys exhibit Curie-Weiss behaviour in the high-temperature regime.