The electron spin resonance (ESR) spectra of tetrakis-dimethylamino-et
hylene (TDAE)-C60 have been observed in the radiofrequency region and
the resonant field - resonance frequency relation has been studied. At
T(c) almost-equal-to 15 K a tremendous increase in intensity and a su
dden line broadening occur as well as a shift of the center of the ESR
line demonstrating the presence of a magnetic transition. A strong no
n-zero absorption is seen below T(c) at zero field supporting the abov
e statement. The values of the local field are however much smaller th
an expected for the case that all C60- spins would order ferromagnetic
ally.