Incommensurate structure of a new Nowotny phase in Fe-Ge system

•A new Nowotny chimney ladder phase is discovered in Fe-Ge system.•The incommensurate of the crystal structure is revealed from electron diffraction analysis.•The composition of the new phase is calculated to be FeGe1.52.

We studied post-annealed Fe-Ge alloy by X-ray diffraction and transmission electron microscopy. A new Nowotny chimney ladder phase has been discovered in such Fe-Ge system. The crystal structure and the composition have been calculated based on selected area electron diffraction. The formation of the incommensurate structure is attributed to the shrinkage of the Ge sublattice to meet the 14 electrons rule.