  We report on magnetotransport measurements on millimetre-large super-lattices
of CoFe nanoparticles surrounded by an organic layer. Electrical properties are
typical of Coulomb blockade in three dimensional arrays of nanoparticles. A
large high-field magnetoresistance, reaching up to 3000 %, is measured between
1.8 and 10 K. This exceeds by two orders of magnitude magnetoresistance values
generally measured in arrays of 3d metals ferromagnetic nanoparticles. The
magnetoresistance amplitude scales with the magnetic field / temperature ratio
and displays an unusual exponential dependency with the applied voltage. The
magnetoresistance abruptly disappears below 1.8 K. We propose that the
magnetoresistance is due to some individual paramagnetic moments localized
between the metallic core of the nanoparticles, the origin of which is
discussed.
