A buried epitaxial IrSi3 layer has been produced in (111) oriented Si by high dose Ir+-implantation (1 MeV, 1.7×1017 Ir+/cm2, 550°C) and subsequent annealing (5 h at 1100°C). Transmission electron microscopy and ion channeling show that the hexagonal IrSi3 prefers to form with its (21
10) plane oriented parallel to Si(111), while its  direction is parallel to either [1
12], , or [21
1]. Thus, the IrSi3 film is made up of three differently oriented crystals, each occupying about 1/3 of the suicide volume.
A dose of 3.5×1016 Ir+/cm2 leads to the formation of a band of large, isolated precipitates. They have the same epitaxial relationship to Si, but the Si(111) plane is no longer the only one to which the (21
10) of IrSi3 is parallel. Instead precipitates are also observed oriented parallel to (111), (111), and (111) in Si in roughly equal numbers. Consequently, there are now 12 possible orientations of IrSi3 crystals. We assume that strain relief and interface area minimization are the main factors suppressing the additional orientations in the continuous IrSi3 films formed by the coalescence of precipitates at higher doses.