Superconductivity and anomalous transport in SrPd2Ge2 single crystals

Abstract

Superconducting ternary germanide SrPd2Ge2 single crystals (T-c = 2.70 K) with a ThCr2Si2-type structure were synthesized using a high-temperature metal flux method. Superconductivity was confirmed by temperature-and magnetic-field-dependent magnetization, electrical resistivity, and heat capacity measurements. Here, weak anisotropy in superconductivity was observed both parallel and perpendicular to the crystallographic c axis. Various superconductivity parameters, such as lower and upper critical fields, the temperature gradient of the upper critical field, and coherence length were estimated, and the upper critical value at T = 0 K was found to be much larger than the value for the polycrystalline sample. In addition, the anomalous temperature dependence of resistivity was observed in a temperature range of T-c (=2.70 K) <= T <= T* (=2.90 K) when a current was applied along the c axis, whereas the only slope change occurred at T* with a current perpendicular to the c axis, prior to a sharp superconducting transition at T-c.