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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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A study by powder X-ray diffraction (using the Rietveld method of structure refinement), 57 Fe Mo ¨ssbauer spectroscopy, and magnetization measurements have shown that YFe 4 Al 8 , although a stable phase at 1070 K (space group I4/mmm, a ) 8.7604(7) Å, c ) 5.0504(5) Å), does not melt congruently. Large single crystals obtained by the Czochralski method from bulk charges containing Y, Fe, and Al in the atomic ratios 1/4/8 have final compositions YFe 4.2(2) Al 7.8(2) (space group I4/mmm, a ) 8.7303(3) Å, c ) 5.0486(2) Å). YFe 4.2 Al 7.8 shows an antiferromagnetic-like transition at T ord ) 100 K, in contrast with YFe 4 Al 8 (T ord ) 180 K). In YFe 4.2 Al 7.8 a distribution of the moduli of the Fe magnetic moments (µ Fe ) is observed between 100 K and ∼50 K. Below 45 K the Fe atoms on the 8f site have two different values of µ Fe and on the 8j sites only one is observed. The relative values of the µ Fe may be understood on the basis of the Fe-Fe intersite exchange interactions.

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