Crystal structure, and physical properties of the novel compounds EuRh sub(3)Ge sub(7) and EuIr sub(3)Ge sub(7)

Two novel compounds, EuRh sub(3)Ge sub(7) and EuIr sub(3)Ge sub(7), have been synthesized by arc melting of the elements and subsequent annealing at 800 & degree C. X-ray structure analyses confirmed for both compounds isotypism with the crystal structure of the ScRh sub(3)Si sub(7)-type (R3c): SC-data for EuRh sub(3)Ge sub(7) (a = 0.78918(2), c = 2.07179(5) nm, R sub(F) = 0.0130) and Rietveld powder data for EuIr sub(3)Ge sub(7) (a = 0.788399(5), c = 2.07583 (2) nm, R sub(F) = 0.0501). Magnetization, heat capacity, thermal expansion and electrical resistivity at various magnetic fields were measured revealing second order phase transitions at 20 K for EuRh sub(3)Ge sub(7), and 87 K for EuIr sub(3)Ge sub(7), respectively. While this transition is clearly antiferromagnetic in the case of EuRh sub(3)Ge sub(7), the nature of this transition remains unclear for EuIr sub(3)Ge sub(7). The evaluation of magnetic susceptibility as well as heat capacity data reveals an intermediate valence state of Eu-ions in both compounds.