  We report an extensive extensive study of the noncentrosymmetric half-Heusler
topological superconductor YPtBi, revealing unusual relation between bulk
superconductivity and the appearance of surface superconductivity at
temperatures up to 3 times the bulk transition temperature. Transport
measurements confirmed the low carrier density of the material and its bulk
superconducting transition, which was also observed in ac susceptibility
through mutual inductance (MI) measurements. However, a weak signature of
superconductivity in the MI measurements appeared much above the bulk
transition temperature, which was further observed in scanning tunneling
spectroscopy. Polar Kerr effect measurements suggest that while the bulk
superconductor may exhibit an unusual nodal superconducting state, only the
surface state breaks time reversal symmetry. Complementary tunneling
measurements on LuPtBi are used to establish the observations on YPtBi, while
density-functional theory (DFT) calculations may shed light on the origin of
this unusual surface state.
