PtPb \(_4\) is a type II superconductor with a bulk critical temperature \(T_{c}\approx 3 \) K and an upper critical field of \(H_{c2}=0.36 \) T. PtPb \(_4\) is related to non-superconducting PtSn \(_4\) , which presents nodal arc states at the surface. Here, we measure the superconducting density of states of PtPb \(_4\) using millikelvin Scanning Tunneling Microscopy (STM). We observe a fully opened superconducting gap of \(\Delta =0.48\) meV similar to expectations from Bardeen, Cooper and Schrieffer (BCS) theory ( \(\Delta _0=1.76k_BT_{c}=0.49 \) meV). Measurements under magnetic fields applied perpendicular to the surface show a spatially inhomogeneous gap structure, presenting superconducting signatures at fields as high as 1.5 T, significantly above \(H_{c2}=0.36 \) T. On some locations, we find that the superconducting density of states does not vanish above \(T_{c}\) . We can find signatures of a superconducting gap up to 5 K. We discuss possible reasons for the observation of superconducting properties above \(T_{c}\) and \(H_{c2}\) , emphasizing the role played by structural defects.
