Superconductivity in the Correlated Pyrochlore Cd₂Re₂O₇

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We report the observation of superconductivity in high-quality Cd₂Re₂O₇ single crystals with room-temperature pyrochlore structure. Resistivity and ac susceptibility measurements establish an onset transition temperature Tconset = 1.47 K with transition width ΔTc = 0.25 K. In applied magnetic field, the resistive transition shows a type-II character, with an approximately linear temperature-dependence of the upper critical field Hc₂. The bulk nature of the superconductivity is confirmed by the specific heat jump with ΔC = 37.9 mJ/mol-K. Using the γ value extracted from normal-state specific heat data, we obtain ΔC/γTc = 1.29, close to the weak coupling BCS value. In the normal state, a negative Hall coefficient below 100 K suggests electron-like conduction in this material. The resistivity exhibits a quadratic T-dependence between 2 and 60 K, i.e., ρ=ρ₀+AT², indicative of Fermi-liquid behavior. The values of the Kadowaki-Woods ratio A/γ² and the Wilson ratio are comparable to that for strongly correlated materials.