Mass enhancement and lone-pair-driven structural distortion in PbC u 3 V 4 O 12

A-site-ordered perovskites (AA^'₃B₄O₁₂) provide a structurally robust platform for exploring correlated-electron behavior, offering unusual opportunities to disentangle the roles of orbital degrees of freedom, bonding interactions, and local structural distortions. In this work, we synthesize a new A-site-ordered perovskite PbCu₃V₄O₁₂ under high-pressure and high-temperature conditions and perform comprehensive structural and physical characterizations. PbCu₃V₄O₁₂ crystallizes in the cubic Im-3 structure, yet its structural parameters deviate markedly from the established ionic-radius trend in the ACu₃V₄O₁₂ (A=Mn, Cu, Ca) series. This deviation reveals local structural modifications driven by the Pb²⁺ lone-pair electrons. The compound exhibits metallic behavior down to at least 8 K and shows a moderately enhanced Sommerfeld coefficient, with density-functional calculations confirming the associated mass enhancement. Comparison of the experimental and theoretical magnetic susceptibilities further indicates an additional contribution from the Stoner mechanism. These results identify PbCu₃V₄O₁₂ as a rare example of a $3d$-electron metallic vanadate with moderate electronic correlations, demonstrating how A-site chemistry and lone-pair-induced local distortions can be used to engineer correlated electronic states in perovskite-related materials.