Synthesis, structural, and electronic properties of Sr1−xCaxPdAs

Abstract

Layered honeycomb intermetallic phases have attracted considerable research interest due to the wide array of exciting physical properties inherent in these materials. Here, we follow the evolution in structure and electronic properties of a relatively unexplored material system, Sr_1−xCa_xPdAs, as the hexagonal PdAs honeycomb layer in SrPdAs distorts into the orthorhombic CaPdAs structure. The Sr-rich compounds (x = 0 to 1/3) form symmetric, hexagonal honeycomb PdAs layers, whereas in the Ca-rich region (x = ½ to 1) the PdAs layers distort into an orthorhombic structure featuring long and short Pd–Pd distances. This distortion occurs when the average Pd–Pd distance falls below 4.21 Å. All compounds are observed to exhibit metallic temperature-dependent resistivity trends. There are no apparent discontinuities indicative of metal-to-insulator transitions and the room temperature resistivity values range from 18 to 180 mΩ cm. In total, this work maps out the structural and electronic phase diagram of Sr_1−xCa_xPdAs compounds.