Symmetry-breaking normal state response and surface superconductivity in topological semimetal YPtBi

Most of the half-Heusler RPtBi compounds (R=rare earth) host various surface states due to spin-orbit coupling driven topological band structure. While recent ARPES measurements ubiquitously reported the existence of surface states in RPtBi, their evidence by other experimental techniques remains elusive. Here we report the angle-dependent magnetic field response of electrical transport properties of YPtBi in both the normal and superconducting states. The angle dependence of both magnetoresistance and the superconducting upper critical field breaks the rotational symmetry of the cubic crystal structure, and the angle between the applied magnetic field and the measurement plane of a plate-like sample prevails. Furthermore, the measured upper critical field is notably higher than the bulk response for an in-plane magnetic field configuration, suggesting the presence of quasi-2D superconductivity. Our work suggests the transport properties cannot be explained solely by the bulk carrier response, requiring robust normal and superconducting surface states to flourish in YPtBi.