Nowotny chimney-ladder(NCL)compounds,MXγ(M: transition metals,and X: groups 13-14 elements),have the potential to exhibit reasonable thermoelectric(TE)performance due to their unique incommensurate crystal structures.The compounds consist of two tetragonal sublattices(subsystems)of [M] and [X],with an identical a-axis length but mutually irrational c-axis lengths.A relatively high TE power factor(~10-3 W/Km)and a satisfactorily low thermal conductivity(~1-2 W/Km)can be simultaneously realised in such an incommensurate structure.