Iron and bismuth usually form immiscible systems. There had been no reports of Fe−Bi bonds in the solid-state literature so far. Still, such compounds could have useful applications, e.g, as additional members of the iron pnictide family of superconductors.

Danna E. Freedman, Northwestern University, Evanston, IL, USA, and colleagues have synthesized the first iron−bismuth binary compound, FeBi₂. To overcome the immiscibility of these two elements, the team used extremely high pressures (> 30 GPa), which were created using a diamond anvil cell (DAC), and a temperature of 1500 K, achieved by laser heating. The reaction was monitored using in situ powder X-ray diffraction.

The newly discovered FeBi₂ crystallizes in the Al₂Cu structure type with the space group I4/mcm. If the pressure is lowered from the initial 30 GPa, the compound is detectable down to about 3 GPa. According to the researchers, this high-pressure approach could be a pathway toward the realization of other new intermetallic materials with chemical bonds never before seen in the solid state.

• Discovery of FeBi₂,
  James P. S. Walsh, Samantha M. Clarke, Yue Meng, Steven D. Jacobsen, Danna E. Freedman,
  ACS Cent. Sci. 2016.
  DOI: 10.1021/acscentsci.6b00287