Growth and Characterization of ROBiS(2) High-Entropy Superconducting Single Crystals

[Image: see text] A series of high-entropy superconductors, ROBiS(2) (R = La + Ce + Pr + Nd + Sm), have been successfully grown in the form of single crystals using CsCl flux. The obtained single crystals have a platelike shape with a size of 0.5–2.0 mm and a thickness of 70–450 μm, and they are cleavable along the c-plane. The c-axis lattice constants of the obtained ROBiS(2) single crystals have similar values of 13.47–13.57 Å. The Ce in the obtained ROBiS(2) single crystals was in a mixed-valence state, comprising both Ce(3+) and Ce(4+). On the other hand, Pr and Sm showed only the trivalent state. The superconducting transition temperatures of ROBiS(2) single crystals were approximately 2–4 K. The superconducting transition temperature and superconducting anisotropies of R-site mixed high-entropy samples increased with a decrease in the mean ionic radius of the R-site. Moreover, a deviation in the tendency to exhibit superconducting properties was observed based on the difference in the R-site mixed entropy. R-site mixed entropy in ROBiS(2) superconductors may affect their superconducting properties.