We examined the temperature-dependent magnetic and structural properties of alpha-HgI2 in the temperature range of 300-400 K using temperature-dependent DC-magnetization, x-ray diffraction (XRD), and x-ray absorption fine structure (XAFS) measurements. DC-magnetization measurements of alpha-HgI2 single crystals show a sudden reduction of diamagnetic susceptibility for T > 350 K. XRD measurements with Rietveld refinements reveal a small but substantial amount of decrease in disorder in both Hg and I sites above 350 K, with neither a structural transition nor vacancies in the temperature range. XAFS demonstrates a shift of the I K edge for T > 350 K but no changes at the Hg L-3 edge. A stronger bonding of Hg-I pairs above 350 K likely affects the electrons in the outermost shells of iodine atoms and enhances the intrinsic paramagnetic properties, thereby producing a reduction in diamagnetism. (C) 2016 Elsevier B.V. All rights reserved.