Antiferromagnetic ordering in (NH3)K3C60 —13C-NMR studies—

13C-NMR experiments have been carried out in order to gain an insight into the change of the electronic state above and below the Metal-Insulator transition at around 40 K in the ammoniated füllende (NH3)K3C60. The antiferromagnetic ordering is unambiguously identified by both a significant increase of 13C linewidth at low temperatures and a distinct drop of the nuclear spin-lattice relaxation rate, 131/T1), just below TW∼45 K.