  Phase selection in deeply undercooled liquids and devitrified glasses during
heating involves complex interplay between the barriers to nucleation and the
ability for these nuclei to grow. During the devitrification of glassy alloys,
complicated metastable structures often precipitate instead of simpler, more
stable compounds. Here, we access this unconventional type of phase selections
by investigating an Al-10%Sm system, where a complicated cubic structure first
precipitates with a large lattice parameter of 1.4 nm. We not only solve the
structure of this "big cubic" phase containing ~140 atoms but establish an
explicit interconnection between the structural orderings of the amorphous
alloy and the cubic phase, which provides a low-barrier nucleation pathway at
low temperatures. The surprising rapid growth of the crystal is attributed to
its high tolerance to point defects, which minimize the short-scale atomic
rearrangements to form the crystal. Our study suggests a new scenario of
devitrification, where phase transformation proceeds initially without
partitioning through a complex intermediate crystal phase.
