Pseudosymmetry in Tetragonal Perovskite SrIrO₃ Synthesized under High Pressure

In this study, we report a tetragonal perovskite structure of SrIrO₃ (P4/mmm, a = 3.9362(9) Å, c = 7.880(3) Å) synthesized at 6 GPa and 1400 °C, employing the ambient pressure monoclinic SrIrO₃ with distorted 6H structure as a precursor. The crystal structure of tetragonal SrIrO₃ was evaluated on the basis of single-crystal and powder X-ray diffraction. A cubic indexing was observed, which was attributed to overlooked superlattice reflections. Weak fractional peaks in the H and K dimensions suggest possible structure modulation by oxygen defects. Magnetization study reveals weak paramagnetic behavior down to 2 K, indicative of the interplay between spin–orbit coupling, electron correlations, and the crystal electric field. Additionally, measurements of electrical resistivity display metallic behavior with an upturn at about 54 K, which is ascribed to weak electron localization and possible structural defects.