P*

Antiperovskie pnictide SrPt₃P shows the highest superconducting transition temperature, T_c, among the 5d element - based compounds, possibly with somewhat strong coupling, 2△₀ /T_c ∼5. While the material itself is quite isotropic, its energy gap structure and pairing state remain uncertain due to the lack of single crystals. Here we report directional measurements of electrical resistivity and London penetration depth in single crystals SrPt₃P. Surprisingly, our results show highly anisotropic nature of the superconducting energy gap.