Fermi Surface and Superconducting Properties of α-IrSn₄, α-RhSn₄, IrGe₄, and RhGe₄ with Trigonal Chiral Structure

We grew single crystals of α-IrSn4 and α-RhSn4 using the Sn-self flux method and those of IrGe4 using the Czochralski method in a tetra-arc furnace, together with polycrystals of RhGe4 under pressure. The obtained single crystals were found to be an enantiopure of the trigonal chiral structures with space groups P3121 (No. 152) or P3221 (No. 154), depending on the samples. Namely, one ingot belongs to P3121 and another ingot belongs to P3221. Single crystalline samples were of high quality, with residual resistivity ρ0 = 0.052 µΩ·cm and residual resistivity ratio RRR = 1250 in α-IrSn4. We confirmed bulk-superconductivity in IrGe4 and RhGe4 from the measurements of the specific heat. The present four compounds are uncompensated metals because the valence electrons are odd in number. The corresponding transverse magnetoresistance indicated saturated behaviors in high magnetic fields, while non-saturated behaviors were observed in the configuration with current \(J\parallel [11\bar{2}0]\) and magnetic field \(H\parallel [\bar{1}100]\), suggesting the existence of open orbits along the [0001] direction. To clarify the Fermi surfaces of these compounds, we conducted de Haas–van Alphen experiments, which showed that the main Fermi surface is a flat ellipsoidal Fermi surface with many arms and is split into two Fermi surfaces, reflecting the noncentrosymmetric (chiral) structure.