Anisotropic superconductivity accompanied by spontaneous symmetry breaking provides key insights into unconventional pairing. Recently, the noble metal alloy ${AB}_4$ has attracted great interest due to the coexistence of superconductivity, topological band structures, and strong spin-orbit interaction. However, the nature of the superconductivity remains elusive. Here, we report signatures of quasi-two-dimensional superconductivity with in-plane anisotropy in a tetragonal ${\mathrm{PtPb}}_4$ crystal, which crystallizes in a geometrically frustrated Shastry-Sutherland (SS) lattice with a unique nonsymmorphic symmetry. Through polar angular-dependent transport measurements, we uncover pronounced out-of-plane anisotropy in the superconducting state, accompanied by evidence of a Berezinskii-Kosterlitz-Thouless transition, indicative of quasi-two-dimensional superconducting behavior. Furthermore, azimuthal angular-dependent measurements reveal a striking in-plane twofold symmetry in both the superconductivity and upper critical field, which disappears in the normal state, suggesting a possible unconventional pairing. Our findings establish a promising platform for further exploring exotic superconducting states such as nematic or topological superconductivity.

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• Superconducting phase transition
• Superconductivity
• Single crystal materials
• Superconductors
• Electrical transport techniques
• Resistivity measurements