Giant Negative Magnetoresistance in GdI2: Prediction and Realization

The electronic structure of the layered d1 compound GdI2 has been examined systematically in view of its relation to other layered d1 systems including superconducting and isostructural 2H-TaS2 and 2H-NbSe2. A van Hove type instability is evident in suitable representations of the Fermi surface. The presence of the half-filled and magnetic 4f level should preclude the possibility of superconductivity. Instead GdI2 orders ferromagnetically at 290(5) K and displays large negative magnetoresistance ~70% at 7 T close to room temperature. This finding provides support to the idea that materials can be searched rationally for interesting properties through high level electronic structure calculations.