  The crystal structure of layered metal IrTe2 is determined using
single-crystal x-ray diffraction. At T=220 K, it exhibits Ir and Te dimers
forming a valence-bond crystal. Electronic structure calculations reveal an
intriguing quasi-two-dimensional electronic state, with planes of reduced
density of states cutting diagonally through the Ir and Te layers. These planes
are formed by the Ir and Te dimers, which exhibit a signature of covalent
bonding character development. Evidence for significant charge
disproportionation among the dimerized and non-dimerized Ir (charge order) is
also presented.
