Magnetic and superconducting properties of CeTX₃ (T: Transition metal and X: Si and Ge) with non-centrosymmetric crystal structure

We grew single crystals of non-centrosymmetric compounds CeTSi₃ and CeTGe₃ (T: transition metal), and studied the magnetic properties by measuring the electrical resistivity, magnetic susceptibility and magnetization. We also studied the effect of pressure on the electronic states in antiferromagnets CeTGe₃ (T: Co, Rh, Ir) by measuring the resistivity under pressure. No noticeable change of the Néel temperature was observed up to 8 GPa in CeRhGe₃ and CeIrGe₃, which are far from the magnetic quantum critical point. On the other hand, the Néel temperature in CeCoGe₃ was strongly decreased as a function of pressure, and pressure-induced superconductivity was observed in the pressure region from 5.4 GPa to about 7.5 GPa. The slope of upper critical field H_c2 at 6.5 GPa is found to be extremely large, with an upturn curvature of H_c2 with decreasing temperature: -dH_c2/dT = 200 kOe/K at the superconducting transition temperature T_sc = 0.69 K, revealing unconventional superconductivity.