RE₇M₄InGe₁₂ (RE = Y, Gd-Er; M = Rh, Os) Quaternary Germanide Series Expansion with Structural Motif Clustering

Intermetallic compounds with two alternating planes of atoms, forming AB layer stacking, are found in numerous prototypes. Yb₇Co₄InGe₁₂ type (adopting tetragonal P4/m space group) belongs to this group, and in this work, we vastly expanded this series by synthesizing compounds with the RE₇M₄InGe₁₂ (RE = Y, Gd, Tb, Dy, Ho, Er; M = Rh, Os) formula by arc melting. Structural analysis and impurity identification by X-ray diffraction and compositional analysis with energy-dispersive X-ray spectroscopy confirm the Yb₇Co₄InGe₁₂-type structure and composition. The anionic network (M-In-Ge) motif geometry and stability are influenced by lanthanoid contraction via RE element substitution. Density functional theory calculations reveal that M substitution, particularly from Ru to Os, Rh, and Pd, shifts the Fermi level, E_F, with electronic structure stabilization occurring with the valence electron-rich metals. These results support previous knowledge of the Yb₇Co₄InGe₁₂ structure type and offer more insight into the tunability of electronic properties in RE₇M₄InGe₁₂ through element substitution. Finally, the structural evolution of Yb₇Co₄InGe₁₂ type among other intermetallic prototypes with similar structural motifs was analyzed using materials informatics tools for crystal structure clustering, which could be expanded to other structural families.