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Abstract

We report on the observation of superconductivity in LaRh2As2, which is the analog without f electrons of the heavy-fermion system with two superconducting phases CeRh2As2 [S. Khim, Science 373, 1012 (2021)10.1126/science.abe7518]. A zero-resistivity transition, a specific-heat jump, and a drop in magnetic ac susceptibility consistently point to a superconducting transition at a temperature of Tc=0.28 K. The magnetic-field temperature superconducting phase diagrams determined from field-dependent ac-susceptibility measurements reveal small upper critical fields μ0Hc2≈12 mT for H∥ab and μ0Hc2≈9 mT for H∥c. The observed Hc2 is larger than the estimated thermodynamic critical-field Hc derived from the heat-capacity data, suggesting that LaRh2As2 is a type-II superconductor with Ginzburg-Landau parameters κGLab≈1.9 and κGLc≈2.7. The microscopic Eliashberg theory indicates superconductivity to be in the weak-coupling regime with an electron-phonon-coupling constant λe-ph≈0.4. Despite a similar Tc and the same crystal structure as the Ce compound, LaRh2As2 displays conventional superconductivity, corroborating the substantial role of the 4f electrons for the extraordinary superconducting state in CeRh2As2. © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.