Crystal structure, and physical properties of the novel compounds EuRh3Ge7 and EuIr3Ge7

Two novel compounds, EuRh3Ge7 and EuIr3Ge7, have been synthesized by arc melting of the elements and subsequent annealing at 800 °C. X-ray structure analyses confirmed for both compounds isotypism with the crystal structure of the ScRh3Si7-type ( R 3 ¯ c ) : SC-data for EuRh3Ge7 (a = 0.78918(2), c = 2.07179(5) nm, RF = 0.0130) and Rietveld powder data for EuIr3Ge7 (a = 0.788399(5), c = 2.07583 (2) nm, RF = 0.0501). ization, heat capacity, thermal expansion and electrical resistivity at various magnetic fields were measured revealing second order phase transitions at 20 K for EuRh3Ge7, and 87 K for EuIr3Ge7, respectively. While this transition is clearly antiferromagnetic in the case of EuRh3Ge7, the nature of this transition remains unclear for EuIr3Ge7. The evaluation of magnetic susceptibility as well as heat capacity data reveals an intermediate valence state of Eu-ions in both compounds.