Crystallographic investigation of Si0.5Ge0.5 single crystals grown by the traveling liquidus-zone (TLZ) method was carried out using an X-ray diffraction method, a back-reflection Laue camera and X-ray rocking curve measurements. X-ray rocking curve of the Si0.5Ge0.5 crystals showed excellent crystallinity: full-width at half-maximum (FWHM) of the (4 4 0) diffraction was 0.009 degrees, which is comparable to that of Si single crystal. Such high-quality Si0.5Ge0.5 bulk crystals were obtained for the first time and showed the superiority of the TLZ growth method for growing alloy bulk crystals. (C) 2007 Elsevier B.V. All rights reserved.