Superconductivity in Rh2Ga9 and Ir2Ga9 without inversion symmetry

Superconductivity with Tc similar or equal to 2 K was discovered in the intermetallic binary compounds Rh2Ga9 and Ir2Ga9. This is the first observation of superconductivity in the Rh-Ga and Ir-Ga binary systems. Both compounds crystallize in a distorted C(o)2Al(9)-type structure (monoclinic, space group: Pc), which lacks spatial inversion symmetry. Specific heat measurements revealed that both compounds are weak-coupling BCS superconductors having an isotropic superconducting gap. Measurements in magnetic fields indicated type-I superconductivity with a critical field H-c(0) similar or equal to 130 Oe for Rh2Ga9 and type-II superconductivity with an upper critical field H-c2(0) similar or equal to 250 Oe for Ir2Ga9.