  Transmission electron microscopy studies of [110] and [111] oriented
FeCr_2S_4 single crystals at different temperatures reveal a structural
transition at low temperatures indicating a cubic-to-triclinic symmetry
reduction within crystallographic domains. The overall crystal symmetry was
found to be reduced from Fd3m to F-43m. The triclinic distortions were
suggested to result from the combined actions of tetragonal distortions due to
the Jahn-Teller active Fe^2+ ions and trigonal distortions due to a
displacement of the Cr^3+ ions in the <111> direction.
