ИСТИНА

Novel ternary intermetallic phase Ce2RuGe was synthesized via arc-melting of the constituents and subsequent annealing at 700 °С. Its crystal structure was determined from the powder X-ray diffraction data collected at room temperature. The compound crystallizes in the orthorhombic structure of a new type: space group P21212, lattice parameters: a = 4.38231(5) Å, b = 4.31823(5) Å, c = 9.91491(15) Å, Z = 2. In the fully ordered unit cell of Ce2RuGe, there are two crystallographic positions for Ce atoms, single site with Ru atoms, and single site with Ge atoms, each with the multiplicity of two. The crystal structure is built of infinite zigzag-like chains of the Ru and Ge atoms, propagating along the [010] direction. The essential feature is a very short interatomic distance between the Ce1 atoms and the Ru atoms being equal to 2.225(2) Å, while the Ce2-Ru distance is of regular length. This structural property gives rise to distinctive physical behavior of the compound that exhibits the coexistence of valence fluctuations associated with unstable 4f shell of the Ce1 ions and a long-range ferromagnetic order that emerges in the Ce2 ions sublattice below TC = 8.5(3) K, as revealed by means of magnetization, heat capacity and electrical resistivity measurements, performed on a polycrystalline sample of Ce2RuGe in wide temperature and magnetic field strength ranges.