Supplementary data are available online at https://www.sciencedirect.com/science/article/pii/S0022459621002449?via%3Dihub#appsec1 .β-AlFeSi has a layered structure composed of FeAlSi blocks and exhibits a rich variety of crystal chemistry. Plate-like/rod-like β-AlFeSi particles formed in Al-based alloys have nontrivial influences on the mechanical performance of the cast parts. Here, we investigate the stability, crystal chemistry and electronic structure of the β-phase using the first-principles density-functional theory (DFT) method. We reveal that Si prefers on the Al1 or Al6 sites, forming stable β-Al4.5SiIFe or β-Al4.5SiVIFe (the Roman numerals represent the Al sites in the Rømming’s labels). This differs from the existing model with a homogeneous Si/Al distribution. Moreover, the calculations also find that stacking of the FeAlSi blocks leads to structural transformations. Electronically β-Al4.5SiFe is anisotropic with a narrow pseudo-band-gap, indicating its unusual physical properties. The obtained information here sheds some light not only on the stability and crystal chemistry of the β-phase as a member of the large family of the Fe-containing intermetallic compounds in Al-based alloys, but also on its potential applications as low-dimensional functional materials.EPSRC (UK) under grant numbers EP/N007638/1 and EP/S005102/1
