Magnetic and transport properties of YBNIGe with a TiNiSi-type structure

The magnetic and transport properties of a single crystal of YbNiGe with an orthorhombic TiNiSi-type structure are presented here. The experimental results indicate that YbNiGe undergoes two successive antiferromagnetic transitions at T_N = 3.6K and T_m = 3.0K at zero field. The magnetic susceptibility and magnetization for the three principal axes show large anisotropy with the magnetic easy-axis along the a-axis, reflecting the orthorhombic crystal structure. The electrical resistivity for the current along the three principal axes shows a metallic behavior with a Kondo increase below around 50K. The magnetic entropy released at T_N is 54% of Rln2 for the Kramers doublet ground state. The Sommerfeld coefficient γ is estimated to be 83.3mJ=mol K² below 1K. The obtained value of A=γ², where A is the coefficient of the T² dependence of the resistivity at low temperatures, is larger than the universal value of the Kadowaki–Woods relation for heavy-fermion systems, i.e., A=γ² = 1.0 × 10⁻⁵µΩ·cm(mol·K=mJ)². Furthermore, this paper discusses the possible nature of two successive antiferromagnetic transitions of YbNiGe in comparison with related isostructural YbTGe compounds.