  Eutectic fibers consisting of an ordered arrangement of LiF fibrils inside a
LiREF4 matrix (RE = Y, Gd) can be grown with the micro-pulling-down method at
sufficiently large pulling rate exceeding 120 mm/h. The distance between
individual fibrils could be scaled down to 1 micrometer at 300 mm/h pulling.
LiF-LiYF4 has stronger tendency to form facetted eutectic colonies than
LiF-LiGdF4, explained by the larger entropy of melting of the former.
