Interface Superconductivity in a Dirac Semimetal NiTe₂

We experimentally investigated charge transport through a single planar junction between a NiTe2 Dirac semimetal and a normal gold lead. At milli-Kelvin temperatures, we observe non-Ohmic dV/dI(V) behavior resembling Andreev reflection at a superconductor-normal metal interface, while NiTe2 bulk remains non-superconducting. The conclusion on superconductivity is also supported by the suppression of the effect by temperature and magnetic field. In analogy with the known results for Cd3As2 Dirac semimetal, we connect this behavior with interfacial superconductivity due to the flat-band formation at the Au-NiTe2 interface. Since the flat-band and topological surface states are closely connected, the claim on the flat-band-induced superconductivity is also supported by the Josephson current through the topological surface states on the pristine NiTe2 surface. We demonstrate the pronounced Josephson diode effect, which results from the momentum shift of the topological surface states of NiTe2 under an in-plane magnetic field.