High-pressure synthesis, crystal structure, and magnetic properties of KSbO(3)-type 5d oxides K(0.84)OsO(3) and Bi(2.93)Os(3)O(11)

5d Solid-state oxides K(0.84)OsO(3) (Os(5.16+); 5d (2.84)) and Bi(2.93)Os(3)O(11) (Os(4.40+); 5d (3.60)) were synthesized under high-pressure and high-temperature conditions (6 GPa and 1500–1700 °C). Their crystal structures were determined by synchrotron x-ray diffraction and their 5d electronic properties and tunnel-like structure motifs were investigated. A KSbO(3)-type structure with a space group of Im-3 and Pn-3 was determined for K(0.84)OsO(3) and Bi(2.93)Os(3)O(11), respectively. The magnetic and electronic transport properties of the polycrystalline compounds were compared with those obtained theoretically. It was revealed that the 5d tunnel-like structures are paramagnetic with metallic charge conduction at temperatures above 2 K. This was similar to what was observed for structurally relevant 5d oxides, including Bi(3)Re(3)O(11) (Re(4.33+); 5d (2.66)) and Ba(2)Ir(3)O(9) (Ir(4.66+); 5d (4.33)). The absence of long-range magnetic order seems to be common among 5d KSbO(3)-like oxides, regardless of the number of 5d electrons (between 2.6 and 4.3 per 5d atom).