Magnetic and superconducting phase diagram of the half-Heusler topological semimetal HoPdBi

We report a study of the magnetic and electronic properties of the non-centrosymmetric half-Heusler antiferromagnet HoPdBi (T_N = 2.0 K). Magnetotransport measurements show HoPdBi has a semimetallic behavior with a carrier concentration n=3.7×10¹⁸ cm^-3 extracted from the Shubnikov-de Haas effect. The magnetic phase diagram in the field-temperature plane has been determined by transport, magnetization, and thermal expansion measurements: magnetic order is suppressed at B_M ∼ 3.6 T for T→0. Superconductivity with T_c∼ 1.9 K is found in the antiferromagnetic phase. Ac-susceptibility measurements provide solid evidence for bulk superconductivity below T_c = 0.75 K with a screening signal close to a volume fraction of 100%. The upper critical field shows an unusual linear temperature variation with B_c2(T→0) =1.1 T. We also report electronic structure calculations that classify HoPdBi as a new topological semimetal, with a non-trivial band inversion of 0.25 eV.