Frontispiece: Hybridization Gap and Dresselhaus Spin Splitting in EuIr4In2Ge4

EuIr4In2Ge4 is a new intermetallic semiconductor that adopts a non-centrosymmetric structure in the tetragonal I (4) over bar 2m space group with unit cell parameters a=6.9016(5)angstrom and c=8.7153(9)angstrom. The compound features an indirect optical band gap E-g=0.26(2)eV, and electronic-structure calculations show that the energy gap originates primarily from hybridization of the Ir 5d orbitals, with small contributions from the Ge 4p and In 5p orbitals. The strong spin-orbit coupling arising from the Ir atoms, and the lack of inversion symmetry leads to significant spin splitting, which is described by the Dresselhaus term, at both the conduction- and valence-band edges. The magnetic Eu2+ ions present in the structure, which do not play a role in gap formation, order antiferromagnetically at 2.5K.