Synthesis, Crystal and Electronic Structure of Ca₄CdIn₂Ge₄: A Quaternary Variant of the Monoclinic Mg₅Si₆ Structure

Reported is the synthesis of a new polar intermetallic phase, Ca 4 CdIn 2 Ge 4 , crystals of which can be readily obtained employing the In‐flux method. The structure and the chemical composition of the new compound are established based on single‐crystal X‐Ray diffraction and energy‐dispersive X‐Ray spectroscopy data. Ca 4 CdIn 2 Ge 4 crystallizes in a monoclinic crystal system with the space group C 2/ m (no. 12) with lattice parameters a = 16.7383(12) Å, b = 4.4235(3) Å, c = 7.4322(5) Å, and β = 106.560(1)°. The structure can formally be classified as a variant of the Mg 5 Si 6 structure type (Pearson symbol mS 22). Considering the InGe and CdGe interactions as mostly covalent, the polyanionic substructure can be rationalized as consisting of ribbons of edge‐shared [InGe 4 ] tetrahedra connected by Ge 2 dimers and bridged by Cd atoms in nearly square‐planar environment. Chemical bonding analysis based on TB‐LMTO‐ASA calculations affirms the notion for covalent character of the GeGe bonding with the dimers. The calculations also show that the bonding in the tetrahedra is more covalent in character than the bonding in square‐planar fragments, with the CaGe interactions being the least covalent among all interactions, though not exactly ionic.