text: FK phase materials have been pointed out for their high-temperature structure and as superconducting materials. Their complex and often non-stoichiometric structure makes them good subjects for theoretical calculations.
  A15, Laves and σ are the most applicable FK structures with interesting fundamental properties.
  The A15 compounds include important intermetallic superconductors such as: NbSn, NbAl, and VGa with applications including wires for high-field superconducting magnets. NbSn is also being investigated as a potential material for fabricating superconducting radio frequency cavities.
  Small extents of σ phase considerably decreases the flexibility and impairment in erosion resistance. While addition of refractory elements like W, Mo, or Re to FK phases helps to enhance the thermal properties in such alloys as steels or nickel-based superalloys, it increases the risk of unwanted precipitation in intermetallic compounds.