Surface superconductivity in a three-dimensional Cd 3 As 2 semimetal at the interface with a gold contact

We experimentally investigate charge transport through a single planar junction between a Cd 3 As 2 Dirac semimetal and a normal Au lead. For nonsuperconducting bulk Cd 3 As 2 samples we observe non-Ohmic d V / d I ( V ) curves, which strongly resemble standard Andreev reflection with a well-defined superconducting gap. Andreev-like behavior is demonstrated for Cd 3 As 2 samples with different surface and contact preparation techniques. We connect this behavior with surface superconductivity due to the flat-band formation in Cd 3 As 2 , which has been predicted theoretically. The conclusion on superconductivity is also supported by the gap suppression by magnetic fields or temperature.