A.M. Strydom

Possible Kondo insulating behaviour in U2Ru2Sn

Abstract The compound U2Ru2Sn is known to crystallize in the tetragonal U3Si2-type structure and is believed to be a weak paramagnet. We report electrical resistivity studies on this compound which seem to indicate semiconducting behaviour at low temperatures and hence a gap formation in this compound. This is evidenced from a sharp rise in the resistivity seen at low temperatures similar to that observed in the so-called Kondo insulators.

Magnetoresistance and thermoelectric power in U2Ni2Sn

Abstract Low-temperature magnetoresistance ( MR ) and thermoelectric power ( S ) measurements are presented for antiferromagnetic U 2 Ni 2 Sn. Appreciable remanence in the MR behaviour is observed. S changes its sign at T N = 24 K from small positive values above T N to large negative values at 6 K where it shows a well resolved minimum.

Magnetoresistivity in uranium-based heavy-fermion compounds

The resistivities ϱ(T) of U2Pt2In and UCu4Pd display NFL characteristics as indicated by linear ϱ(T) behaviour at low temperatures, but this linear relationship is broken down by applying at 7.5 T magnetic field. (U0.9Th0.1)2Pt2ln displays a knee at 19 K in its zero-field resistivity but the knee is smeared out by application of a magnetic field.

Low-temperature transport properties of U2Rh2Sn and U2Fe2Sn

Magnetoresistivity measurements of polycrystalline U2Rh2Sn in an applied magnetic field of 8.29 T reveal a sharp minimum at the antiferromagnetic transition temperature TN≊20 K. The thermoelectric power of U2Rh2Sn exhibits negative values for temperatures T⪯24 K. At T≊4 K, a large decrease in resistivity with lowering of temperature is observed for polycrystalline U2Fe2Sn. This anomaly originates from the occurrence of free tin on the grain boundaries of the sample giving a decrease in resistivity as a result of superconductivity.

Anomalous low-temperature properties of U2Ni2In and U2Rh2In

Abstract Anomalous properties are observed at low temperatures for U2Ni2In and U2Rh2In. The resistivity of antiferromagnetic (AF) U2Ni2In shows an upturn for T≤4 K which is ascribed to Kondo scattering. Magnetization isotherms of U2Rh2In for T≤3.5 K show a metamagnetic-like upturn for fields B>2 T . A broad peak centered at T=6 K is observed in the susceptibility of this compound. These results suggest the presence of magnetic correlations at low temperatures in U2Rh2In.

Resistivity and magneto-resistivity of antiferromagnetic U2Pt2Sn

Abstract The temperature dependence of the resistivity, ϱ(T) and magnetoresistivity (T ≥ 1.5 K, B ≤ 8 T) of polycrystalline U2Pt2Sn are reported. ϱ(T) shows maxima at 12 K and 45 K and a minimum at 19 K. A minimum is observed in d ϱ(T) d T at the Neel temperature of 15 K. The magnetoresistance at low temperatures is negative and below TN it displays a step-like decrease in an applied field of about 2 T indicating the presence of a phase transition.

Non-Fermi liquid studies in (U,Th)Pd2X3 compounds (X = Al, Ga)☆

Abstract Resistivity ϱ ( T ) and magnetoresistivity results are reported for several U 1− x Th x Pd 2 Al 3 compounds and for U 0.3 Th 0.7 Pd 2 Ga 3 . Non-Fermi liquid behaviour is observed for U 0.4 Th 0.6 Pd 2 Al 3 as evidenced from a linear temperature dependence of ϱ ( T ) at low temperatures. Application of a magnetic field changes the resistivity to a ϱ = ϱ 0 − cT n dependence.

Electrical resistivity of (UxTh1 − x)2Pt2In

Abstract Measurements on the temperature dependence of resistivity (ϱ) of polycrystalline specimens of the heavy-fermion compound U 2 Pt 2 In and of thorium-substituted (U x Th 1 − x ) 2 Pt 2 In are reported. For U 2 Pt 2 In, a linear curve of ϱ ( T ) is observed for 15 K > T > 1.5 K, while the x = 0.9 alloy displays a knee at T = 20 K followed upon cooling by a quadratic decrease of ϱ ( T ).

Anomalous electrical resistivities of U2M2Sn (M Fe, Ni or Rh)

Abstract Temperature dependencies of the electrical resistivity ϱ of the tetragonal stannides U2M2Sn are reported for as-prepared and annealed samples. Room temperature values of ϱ = 350 μΩ- cm for U2Ni2Sn, 500 μΩ-cm for U2Rh2Sn and 2000 μΩ-cm for U2Fe2Sn are observed. Anomalies are observed at 23 K for both the U2Rh2Sn and U2Ni2Sn samples.

Antiferromagnetic ordering in NdAuGe compound

The compound NdAuGe was investigated by means of electrical resistivity, ρ(T), magnetic susceptibility, χ(T), magnetization, σ(μ0H), and specific heat, Cp(T), measurements. Powder X-ray diffraction studies confirm a hexagonal LiGaGe-type structure with space group P63mc (No. 186). ρ(T) data show normal metallic behaviour and a tendency toward saturation at higher temperatures. The low temperature ρ(T) data indicate a phase transition around 3.8 K. The low field dc χ(T) data show an antiferromagnetic anomaly associated with a Neel temperature at TN = 3.7 K close to the phase transition observed in ρ(T) results. At higher temperatures, χ(T) follows the paramagnetic Curie-Weiss behaviour with an effective magnetic moment μeff=3.546(4) μB and a paramagnetic Weiss temperature of θp=−6.1(4) K. The value obtained for μeff is close to the value of 3.62 μB expected for the free Nd3+-ion. σ(μ0H) shows a linear behaviour with applied field up to 3 T with an evidence of metamagnetic behaviour above 3 T. Cp(T) confirm...