Abstract
The structure of the decagonal approximant Al3Mn phase, which has been described in terms of the aggregation of clusters until now, is interpreted as a modulated crystal structure. It contains everywhere the same stacking motif as observed in icosahedral approximants such as the μ- and λ-Al4Mn phases as reported by Uchida and Matsui (2000, Acta crystallogr., B, 56, 654) and is suggested to be a crystal subjected to a shear transformation on the unit-cell scale.