The magnetic field dependence of the spin-lattice relaxation rate 1/T 1 of 119 Sn in CeNiSn has been measured down to 20 mK in a field range of 0.2-8 T. (T 1 T) Ϫ1 is constant below 1 K, which depends on the external field in such a manner that its value stays constant to 2 T, while it increases linearly with the field up to 8 T. It is shown that this magnetic field dependence of (T 1 T) Ϫ1 is well explained by the simple scenario that the quasiparticle density of states at the Fermi level is produced by the Zeeman splitting of the up-and down-spin bands, keeping its V-shaped gapped structure unchanged for fields less than 8 T. The present experiment has elucidated that CeNiSn is in a semimetallic ground state with a low carrier density and the application of a magnetic field exceeding 2 T turns out to supply effective carriers. ͓S0163-1829͑96͒09933-X͔ PHYSICAL REVIEW B

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We present thermal-conductivity and thermopower S measurements on high-quality single crystalline CeNiSn along the three crystallographic axes a, b, and c in the temperature range between 100 mK and 7 K and in magnetic fields up to 8 T applied along the a axis. Both and S are highly anisotropic. However, characteristic features that may be attributed to the opening of a pseudogap in the electronic density of states ͑DOS͒ at the Fermi energy below 10 K are seen for all three crystallographic directions. These features are strongly suppressed by a magnetic field of 8 T applied along the a axis. At the lowest temperatures we have evidence for the presence of a residual metallic DOS at , again for all three directions. The saturation of the reduced Lorenz number L/L 0 to a value distinctly higher than one is an interesting feature which deserves further investigation.