We present the temperature dependence of the lattice constants (a, b, c) of beta-FeSi2 single crystals at low temperatures. a showed the largest temperature dependence of 0.14% and the relationship of a>c>b did not change at 8-300 K. The linear thermal expansion coefficients a showed remarkable anisotropy. alpha along the a-axis (alpha parallel to a) was much larger than (alpha parallel to b) and (alpha parallel to c), and showed negative thermal expansion at temperatures below 60 K. From these results, we estimated the temperature dependence of the lattice mismatches at beta-FeSi2/Si heterojunctions. (C) 2004 Elsevier B.V. All rights reserved.