The AuIn2 phase formed at the initial stage of alloying of gold-indium films by evaporation of indium onto an Au[111] matrix was investigated by selected area electron diffraction. It was found that the AuIn2 lattice has a preferred orientation for the Au matrix; this can be explained by the atomic arrangement and orientation deviation of the AuIn2 lattice. The lattice orientation relation between the AuIn2 phase and the Au matrix is determined to be <((1)over bar 10)>(AuIn2)parallel to(111)(Au) and [001](AuIn2)parallel to<[(1)over bar 10]>(Au).