We show that in agreement with the ternary Fe-Ga-As phase diagram, the solid-state interdiffusions in epitaxial Fe/GaAs(0 0 1) heterostructures lead, at a temperature of approximately 500 degreesC, to the formation of thermodynamically stable Fe3GaAs/GaAs(0 0 1) contacts quite similar to the well-known silicide/Si ones. The Fe3GaAs films are made of grains epitaxial on GaAs with a well-defined interface. Their magnetic and electrical properties make Fe3GaAs on GaAs an attractive metallization scheme for future magnetoelectronic devices. The results we report concern (25 or 80 nm Fe)/GaAs(0 0 1) heterostructures annealed at 480 and 500 degreesC for 10 min and characterized ex situ by He+ Rutherford backscattering and ion channeling, X-ray diffraction, transmission electron microscopy and alternating gradient field magnetometry. (C) 2003 Elsevier B.V. All rights reserved.