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The recent more thorough reinvestigation of the U-Ge system has finally established the existence of five compounds with the chemical formulae U(5)Ge(4), UGe, U(3)Ge(5), UGe(2) and UGe3. Here we add another compound UGe(2-x), existing in a homogeneity range of 0.30<x<0.35, and crystallizing in the defect tetragonal ThSi(2)-type structure. This compound is a ferromagnet with T(C) = 47K. For all these compounds we have revised earlier measured magnetic properties such as the electrical resistivity at 0 T and in applied magnetic fields up to 8 T. We have found no superconducting properties for U(5)Ge(4) down to 20mK, which was claimed earlier. The most striking features found for both ferromagnets UGe(2-x) (ThSi(2)-type phase) and UGe(2) (ZrGa(2)-type phase) are their temperature dependences of the magnetoresistivity (MR). At low temperatures the MRs for both these phases are large and positive which, above 10 and 15K respectively, change sign to negative. The largest negative values of MR were found not at the corresponding T(C) values but at the characteristic temperature T{1}, which is an inflection point T(i) of the p(T) curve; this is attributed to be a measure of the spin fluctuation temperature T(sf).

Additional information

Authors: NOEL H, Laboratoire de Chimie du Solide et Inorganique Moleculaire, Unite Mixte de Recherche associee au CNRS, Rennes (FR);TROC R, W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw (PL);NOËL H, Laboratoire de Chimie du Solide et Inorganique Moléculaire, Unité Mixte de Recherche associée au CNRS, Rennes (FR);BOULET P, European Commission, Joint Research Centre, Institute for Transuranium Elements, Karlsruhe (DE)
Bibliographic Reference: An article published in: Philosophical Magazine B, 2002, Vol 82, No 7, Pp.805-824
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