  We provide evidence that high-pressure high-temperature (2.5 GPa and 1040 K)
treatment of mixtures of iron with fullerene powders leads to the complete
transformation of iron into iron carbide Fe$_3$C. The comparison of the
magnetic properties (Curie temperature and magnetic moment) of the here studied
samples and those for the ferromagnetic polymer Rh-C$_{60}$ indicates that the
main ferromagnetic signal reported in those samples is due to Fe$_3$C and not
related to the ferromagnetism of carbon as originally interpreted. Taking into
account the results obtained in this study the original paper on ``Magnetic
carbon" (Nature {\bf 413}, 716 (2001)) was recently retracted.
