A Monoclinic Variant of ThCr₂Si₂-Type BaAg₂Sb₂: Electronic Structure and Physical Properties

A monoclinic variant of the ThCr₂Si₂-type structure of BaAg₂Sb₂, with the Pearson symbol mC10, has been discovered. Its crystal structure was determined by single-crystal X-ray diffraction, with space group C2/m (No. 12), and lattice parameters a = 12.441(4) Å, b = 4.790(2) Å, c = 4.876(2) Å, β = 112.88(1)°, and V = 268.8(6) ų. It features tetragonally coordinated Ag₂Sb₂ layers that are distorted and stacked along the crystallographic a-axis, with a strong interlayer Sb-Sb bond. Transport measurements reveal a non-negligible magnetoresistivity of up to 18%, with cusp-like behavior. Electron-dominated charge carriers over a broad temperature range are also verified by Hall measurements. Moreover, temperature-dependent resistivity behavior exhibits a small deviation from the conventional Bloch-Grüneisen model, which is likely due to the brink of a possible Lifshitz transition, as revealed by first-principles calculations.