Crystals of Ce ؉4 Mn ؉2
2 Ge 4 O 12 and Gd ؉3 Mn ؉3 Ge 2 O 7 were obtained during the exploration of the quaternary Ln-Mn-Ge-O system. Their structures have been determined by single-crystal X-ray diffraction: CeMn 2 Ge 4 O 12 crystallizes in the tetragonal space group P4/nbm with a ؍ 9.816(1) A > , c ؍ 4.888(1) A > , Z ؍ 2, and R ؍ 0.026 while GdMnGe 2 O 7 crystallizes in the orthorhombic space group A222 with a ؍ 4.735(1) A > , b ؍ 7.839(2) A > , c ؍ 13.500(3) A > , Z ؍ 4, and R ؍ 0.048. Both frameworks are built up from the same polyhedra, i.e., LnO 8 antiprisms, MnO 6 octahedra, and GeO 4 tetrahedra. CeMn 2 Ge 4 O 12 is isotypic with SrNa 2 P 4 O 12 ; the GeO 4 tetrahedra are linked into Ge 4 O 12 rings located between layers of CeO 8 and MnO 6 polyhedra sharing edges. On the other hand, GdMnGe 2 O 7 exhibits a novel quasione-dimensional lattice which might be ascribed to the Jahn-Teller nature of the Mn ؉3 ion. The structure consists of chains of MnO 6 octahedra alternating with parallel chains of GdO 8 antiprisms forming layers linked together through Ge 2 O 7 groups. A structural comparison with fluorite-related compounds as well as CeMn 2 Ge 4 O 12 will be discussed.