Synthesis and physical properties of Ce\(_2\)Rh\(_{3+\delta}\)Sb\(_4\) single crystals

Millimeter-sized Ce\(_2\)Rh\(_{3+\delta}\)Sb\(_4\) (\(\delta\approx 1/8\)) single crystals were synthesized by a Bi-flux method and their physical properties were studied by a combination of electrical transport, magnetic and thermodynamic measurements. The resistivity anisotropy \(\rho_{a,b}/\rho_{c}\sim2\), manifesting a quasi-one-dimensional electronic character. Magnetic susceptibility measurements confirm \(\mathbf{ab}\) as the magnetic easy plane. A long-range antiferromagnetic transition occurs at \(T_N=1.4\) K, while clear short-range ordering can be detected well above \(T_N\). The low ordering temperature is ascribed to the large Ce-Ce distance as well as the geometric frustration. Kondo scale is estimated to be about 2.4 K, comparable to the strength of magnetic exchange. Ce\(_2\)Rh\(_{3+\delta}\)Sb\(_4\), therefore, represents a rare example of dense Kondo lattice whose Ruderman-Kittel-Kasuya-Yosida exchange and Kondo coupling are both weak but competing.