Abstract
On the basis of a concept of inhomogeneous linear structure series a model for the “Chimney-Ladder”Nowotny phases is proposed. All the phases can be explained as members of a structural series of general formulaT p+2q+3r B 2p+2q+4r ,T-transition metal of 5–7 groups,B-Al, Ga, Si, Ge, Sn. The real and possible hypothetical members of this series are described by the symmetry of 21 monoclinic, orthorhombic and tetragonal space groups. The structure types for Tc4Si7 and Mo9Ge16 have been proposed.