Robust Two-Dimensional Surface Superconductivity and Vortex Lattice in the Weyl Semimetal γ-PtBi_{2}

The layered compound γ-PtBi_{2} is a topological semimetal with Fermi arcs at the surface joining bulk Weyl points. Recent work has found signatures of surface superconductivity consisting of gap openings compatible with a critical temperature orders of magnitude larger than the bulk value. However, no superconducting vortices have been identified, raising questions about the robustness of the phase coherence. Here, we use very low temperature STM and find robust superconductivity with T_{C}=2.9  K and H_{C2}≈1.8  T linked to the Fermi arcs. We observe quantized superconducting vortices and the Josephson effect, demonstrating two-dimensional macroscopic quantum phase coherence.