Synthesis,crystal structure and magnetic properties of Yb8Ag18.5Al47.5, Yb2Pd2Cd and Yb1.35Pd2Cd0.65

We report the synthesis of three new Yb-based compounds, Yb₈Ag_18.5Al_47.5 (Yb₈Cu₁₇Al₄₉-type, tetragonal tI74–I4/mmm), Yb₂Pd₂Cd (Mo₂B₂Fe-type, tetragonal tP10-P4/mbm) and Yb_1.35Pd₂Cd_0.65 (MnCu₂Al-type, cubic cF16–Fm3¯m). 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 Yb₈Ag_18.5Al_47.5 and Yb_1.35Pd₂Cd_0.65. The 4f levels of the Yb ions are appreciably hybridised in Yb₈Ag_18.5Al_47.5 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 ≈600 mJ/mol K² 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 Yb_1.35Pd₂Cd_0.65 and order magnetically near 1.4 K.