YbNiSi3 : An antiferromagnetic Kondo lattice with strong exchange interaction

We report on the structural, thermodynamic, and transport properties of high quality single crystals of YbNiSi3 grown by the flux method. This compound crystallizes in the SmNiGe3 layered structure type of the Cmmm space group. The general physical behavior is that of a Kondo lattice showing an antiferromagnetic ground state below TN=5.1 K. This is among the highest ordering temperatures for a Yb-based intermetallic, indicating strong exchange interaction between the Yb ions, which are in or very close to +3 valency based on the effective moment of 4.45μB/f.u. The compound has moderately heavy-electron behavior with a Sommerfeld coefficient of 190 mJ/mol K2. Resistivity is highly anisotropic and for I ⊥ b exhibits the signature logarithmic increase below a local minimum, followed by a sharp decrease in the coherent/magnetically ordered state, resulting in a residual resistivity of 1.5 μΩ cm and a residual resistivity ratio of 40. Fermi-liquid behavior consistent with a ground-state doublet is clearly observed below 1 K