The array of In-Bi heterodimers on the Si(100) surface

•In and Bi atoms form heterogenous In-Bi dimers on the Si(100).•In-Bi heterodimers are arranged into 2  ×  4 lattice with three dimers per unit cell.•Inside the unit cell, an asymmetric In-Bi dimer may have two orientations; the orientation of a dimer has no obvious correlation to the neighboring one.•The surface reconstruction displays semiconducting properties with small Rashba-type spin splitting of surface states.