The temperature dependence of the methyl proton NMR shift of a TDAE-C-
60 single crystal follows a Curie-Weiss law above T-C with a positive
Curie temperature T-C approximate to 12 K as expected for the case of
a ferromagnetic transition. Below T-C the shifts are proportional to t
he magnetization and saturate below 10 K. The internal field at the TD
AE protons amounts at 6 K to 600 G and exceeds by an order of magnitud
e the internal field determined by electron-spin resonance at the C-60
(-) ions. The result shows that in addition to the direct C-60(-)-C-60
(-) interactions which seem to be of antiferromagnetic nature, a part
of the exchange coupling between the C-60(-) ions is mediated by the T
DAE(+) groups. It is this indirect coupling which might give rise to t
he Dzyaloshinsky-Moriya term in the spin Hamiltonian which is responsi
ble for weak ferromagnetism in this system.