Iron tetraboride FeB4
In a large international collaboration the novel boride FeB4 was investigated . This compound originates from a high-pressure high-temperatures synthesis. Remarkably, its existence and its superconductivity were successfully predicted before the synthesis of the actual samples. The obtained single crystals proved to be highly incompressible and superconducting below a Tc of 2.9 K. Moreover, the compound is a rare example of a conventional (electron-phonon coupling) superconductor containing high amounts of iron.
We have also reported in detail on the synthesis and properties of the superconducting borides TaRuB and NbOsB with a quasi-one dimensional electronic structure . Thanks to our home-built adiabatic demagnetization stage for electrical resistivity measurements down to 0.07 K in a standard PPMS we could discover and investigate the superconductivity of NbOsB.