Diamond seed crystals were treated with Fe3C Powders under high temperature and high pressure (HPHT). AFM images reveal that high quality homo-epitaxial diamond have been successfully grown on the diamond seed. The homoepitaxial grown diamond film was also confirmed by laser Raman spectra and a net positive weight gain of the diamonds. It was suggested that homo-epitaxial diamond film could be formed through decomposition of iron carbide under HPHT. This study provides direct evidence for diamond formation directly through decomposition of transition metal carbide, and sets up a very effective way to realize diamond growth different from traditional HPHT method using graphite as a carbon source. (C) 2002 Published by Elsevier Science B.V.