Collapse of the Pseudogap in Kondo Semimetal CeNiSn Observed by Magnetization and Magnetoresistance Measurements in High Magnetic Fields up to 65 T

The effect of magnetic field on the pseudogap in the Kondo semimetal CeNiSn has been reinvestigated by the measurement of magnetization and longitudinal magnetoresistance in pulsed high magnetic fields applied along the principal crystallographic directions of the orthorhombic structure. By extending the field range up to 65 T, metamagnetic behaviors at 45 and 60 T are observed for the first time along the easy magnetization direction of a -axis. No anomaly is found, on the other hand, along the b - and c -axes up to 55 T. The magnetoresistance along the a -axis exhibits the minimum at about 30 T and increases above 40 T, which is in accord with the anomalous increase of the magnetization. By contrast, the magnetoresistance along the b - and c -axes shows only a monotonous decrease above 10 T. These results are discussed in terms of a Zeeman splitting of the double-gapped density of states derived from the anisotropic hybridization-gap model.