  Single crystals of the novel strontium osmate Sr3Os4O14 have been grown by
the hydrothermal method using opposed anvil high-pressure and high-temperature
technique. The reaction took place in sealed gold capsules at 3 GPa and a
temperature of 1100 C, with water acting as a solvent. The employed method
yields up to 1 mm crystals with quite uncommon double-terminated morphologies.
The crystal structure was identified as tetragonal by single-crystal X-ray
diffraction, with lattice parameters a = 12.2909(8) A and c = 7.2478(5) A. The
structural analysis suggests P42nm or P42/mnm as a possible space group. In
general, the structure belongs to the pyrochlore type and is composed of a
network of symmetrically arranged OsO6 octahedra. Resistivity measurements
evidence a metallic behavior, accompanied by a temperature-independent
paramagnetism. Heat capacity measurements reveal a slightly enhanced value of
the Sommerfeld coefficient 34 mJ/mol K2. Superconductivity has not been
observed down to 2 K.
