Anisotropic superconducting properties of Pd₃Bi₂Se₂ single crystals

The Parkerite-type transition-metal chalcogenides have been known for their intriguing properties such as charge density wave, superconductivity, and intercalation reactions. Here, we report electrical transport down to 1.8 K and tunnel diode oscillator (TDO) measurements down to 450 mK on high quality single crystalline Pd₃Bi₂Se₂ adopting the Parkerite structure. The temperature dependence of the electrical resistivity shows typical metallic behavior. Superconductivity is observed with an onset temperature of ~0.82 K via the TDO measurements. By measuring the temperature dependence of the TDO resonant frequency in various applied fields, the phase diagrams are constructed for both in-plane and out of plane directions. The ratio of the upper critical field H_c2(in-plane)/H_c2(out of plane) is found to be 1.75, indicating a weak anisotropic nature of the superconductivity in Pd₃Bi₂Se₂. This low value of the anisotropy is unexpected considering the layered monoclinic structure of Pd₃Bi₂Se₂ suggesting that the bonding along the out of plane direction is reasonably strong in this material.