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 <i>mC</i>10, has been discovered. Its crystal structure was determined by single-crystal X-ray diffraction, with space group <i>C</i>2/<i>m</i> (No. 12), and lattice parameters <i>a</i> = 12.441(4) Å, <i>b</i> = 4.790(2) Å, <i>c</i> = 4.876(2) Å, <i>β</i> = 112.88(1)°, and <i>V</i> = 268.8(6) ų. It features tetragonally coordinated Ag₂Sb₂ layers that are distorted and stacked along the crystallographic <i>a</i>-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.