Superconductivity in a breathing kagome metals ROs2 (R = Sc, Y, Lu)

We have successfully synthesized three osmium-based hexagonal Laves compounds R Os 2 ( R = Sc, Y, Lu), and discussed their physical properties. LeBail refinement of pXRD data confirms that all compounds crystallize in the hexagonal centrosymmetric MgZn 2 -type structure ( P6 3 /mmc , No. 194). The refined lattice parameters are a = b = 5.1791(1) Å and c = 8.4841(2) Å for ScOs 2 , a = b = 5.2571(3) Å and c = 8.6613(2) Å for LuOs 2 and a = b = 5.3067(6) Å and c = 8.7904(1) Å for YOs 2 . R Os 2 Laves phases can be viewed as a stacking of kagome nets interleaved with triangular layers. Temperature-dependent magnetic susceptibility, resistivity and heat capacity measurements confirm bulk superconductivity at critical temperatures, T c , of 5.36, 4.55, and 3.47 K for ScOs 2 , YOs 2 , and LuOs 2 , respectively. We have shown that all investigated Laves compounds are weakly-coupled type-II superconductors. DFT calculations revealed that the band structure of R Os 2 is intricate due to multiple interacting d orbitals of Os and R . Nonetheless, the kagome-derived bands maintain their overall shape, and the Fermi level crosses a number of bands that originate from the kagome flat bands, broadened by interlayer interaction. As a result, R Os 2 can be classified as (breathing) kagome metal superconductors.