Kondo-lattice behaviour of CeNi9Si4

We have studied the crystal chemistry, thermodynamic and transport properties of ternary compounds RNi9Si4 with R=La and Ce. The Rietveld refinement of the X-ray diffraction pattern revealed a tetragonal crystal structure (space group I4/mcm) that is derived from the cubic NaZn13 structure type. In the case of CeNi9Si4 resistivity, magnetic susceptibility and specific heat measurements reveal Kondo-lattice behaviour with a T2 temperature dependence of the electrical resistivity, an enhanced Pauli susceptibility χ0=5x10-3 emu/mol and a Sommerfeld value γ=155 (5) mJ/mol K2. The magnetic susceptibility and specific heat contribution is well described by the Coqblin-Schrieffer model with a fully degenerate J=5/2 ground state and a characteristic temperature T0≅180 K. LaNi9Si4 exhibits simple Pauli paramagnetic, metallic behaviour with a Sommerfeld value γ=33 mJ/mol K2