An alloy semiconductor Si1-xGex (x similar to 0.5) crystal was grown by the TLZ method in microgravity. Ge concentration was 48.5 +/- 1.5 at% for the whole region of 10 mm diameter and 17.2 mm long crystal. Compositional uniformity was established but the average concentration was a little deviated from the expected 50 at%. For further improving compositional uniformity and for obtaining Si0.5Ge0.5 crystals in microgravity, growth conditions were relined based on the measured axial compositional profile. In determining new growth conditions, difference in temperature gradient in a melt, difference in freezing interface curvature, and difference in melt back length of a seed between microgravity and terrestrial growth were taken into consideration. (C) 2013 Elsevier B.V. All rights reserved.