High-Magnetic-Field Studies of the Kondo Semiconductor CeNiSn(Transport and Fermiology)

The Kondo-lattice compound CeNiSn behaves as a narrow-gap semiconductor at low temperatures below 7 K. The effect of magnetic field on the gapped state of this compound has been studied by the measurements of magnetization, magnetoresistance and specific heat on a single-crystalline sample. A weak metamagnetic transition and very large negative magnetoresiostance are observed only when a magnetic field higher than 13 T is applied along the α axis of the orthorhombic structure. These results show that the pseudogap is suppressed anisotropically by the magnetic field. The collapse of the gap is accompanied with the evolution of a polarized heavy-fermion state