The internal streaking contrast within ion beam synthesized &bgr;‐FeSi2(&bgr;) grains has been studied. The results show that this internal streaking contrast is caused by the interfaces between coexistent &bgr; order domains (ODs) which are 90° oriented to one another around [200]&bgr;. The interface between adjacent ODs is (200)&bgr;. The mechanism for the formation of order domain boundaries (ODBs) is attributed to the impingements of separately nucleated growing silicide nuclei during the process of ion implantation and subsequent thermal annealing. ©1995 American Institute of Physics.