Synthesis, crystal structure and magnetic properties of Yb8Ag18.5Al47.5, Yb2Pd2Cd and Yb-1.35Pd2Cd0.65

We report the synthesis of three new Yb-based compounds, Yb8Ag18.5Al47.5 (Yb8Cu17Al49-type, tetragonal tI74-14/mmm), Yb2Pd2Cd (Mo2B2Fe-type, tetragonat tP10-P4/mbm) and Yb1.35Pd2Cd0.65 (MnCu2Al-type, cubic cF16-Fm (K) over barm). The crystal symmetry of these compounds has been determined and the complete structural characterisation carried out by single crystal and powder diffraction techniques. Two symmetry in-equivalent sites are available for the Yb ions in Yb8Ag18.5Al47.5 and Yb1.35Pd2Cd0.65. The 4f levels of the Yb ions are appreciably hybridised in Yb8Ag18.5Al47.5 and to a lesser extent in Yb2Pd2Cd as inferred from the magnetisation and heat capacity data. Signatures of heavy fermion behaviour are observed in the heat capacity data of Yb2Pd2Cd in which the heat capacity, C/T, increases at low temperatures attaining a value of approximate to 600 mJ/mol K-2 at 1.8 K. The electrical resistivity of Yb2Pd2Cd follows a linear variation with temperature, T, between 1.4 and 5 K, thus indicating a possible non-Fermi liquid behaviour. In contrast, Yb ions are trivalent in Yb1.35Pd2Cd0.65 and order magnetically near 1.4 K. (c) 2006 Elsevier B.V. All rights reserved.