  The search for nontrivial superconductivity in novel quantum materials is
currently a most attractive topic in condensed matter physics and material
science. The experimental studies have progressed quickly over the past couple
of years. In this article, we report systematic studies of superconductivity in
Au2Pb single crystals. The bulk superconductivity (onset transition
temperature, Tconset= 1.3 K) of Au2Pb is characterized by both transport and
diamagnetic measurements, where the upper critical field Hc2 shows unusual
quasi-linear temperature dependence. The superconducting gap is revealed by
point contact measurement with gold tip. However, when using tungsten (W) tip,
which is much harder, the superconducting gap probed is largely enhanced as
demonstrated by the increases of both Tconset and upper critical field (Hc2).
This can be interpreted as a result of increase in density of states under
external anisotropic stress imposed by the tip, as revealed by first-principles
calculations. Furthermore, novel phase winding of the pseudospin texture along
k-space loops around the Fermi energy is uncovered from the calculations,
indicating that the observed superconductivity in Au2Pb may have nontrivial
topology.
