ИСТИНА

The discovery of ferroarsenide superconductors in 2008 immediately attracted attention to functional properties of various compounds of iron. In this paper, we will present and discuss several different compounds of iron with intriguing properties that appear owing to strong electron correlations. We will first focus on layered complex tellurides structurally resembling ferroarsenide superconductors but displaying a framework of short Fe–Fe contacts that evoke metallic properties and peculiar magnetic behavior including a sizable magnetocaloric effect. We will compare these tellurides with intermetallic iron semiconductors rich in p-metals, such as FeGa3. They are promising thermoelectric materials, which properties are governed by strong d–p interactions between iron and a p-element that open a band gap in the electronic structure near the Fermi level. As an intermediate between these two opposites we will bring to consideration iron germanides that possess atypically complicated antiferromagnetic structures due to comparable contribution of d–d and d–p interactions to their electronic structure. We will discuss the underlying physics of these properties and the unique role of iron in them.