A comparison between the framework structures of (a), (b) SU-66 and (c), (d) SU-61 in polyhedron representation. (Left) Both structures are constructed of layers of Ge10 clusters in the 63 net. Half of the Ge10 clusters in SU-66 are oriented as those in SU-61. The solid circle indicates a Ge10 cluster that is in the same orientation in both SU-66 and SU-61, while the dashed circle outlines a Ge10 cluster that has different rotational orientation between the two structures. (Right) The layers stack and are connected forming one-dimensional channels. Octahedra are shown in red and tetrahedra in green.