  Structural rearrangement of liquid Bi in the vicinity of the melting point
has been proposed due to the unique temperature invariant sound velocity
observed above the melting temperature, the low symmetry of Bi in the solid
phase and the necessity of overheating to achieve supercooling. The existence
of this structural rearrangement is examined by measurements on supercooled Bi.
The sound velocity of liquid Bi was measured into the supercooled region to
high accuracy and it was found to be invariant over a temperature range of ca.
60 degrees, from 35 degrees above the melting point to ca. 25 degrees into the
supercooled region. The structural origin of this phenomenon was explored by
neutron diffraction structural measurements in the supercooled temperature
range. These measurements indicate a continuous modification of the short range
order in the melt. The structure of the liquid is analyzed within a
quasi-crystalline model and is found to evolve continuously, similar to other
known liquid pnictide systems. The results are discussed in the context of two
competing hypotheses proposed to explain properties of liquid Bi near the
melting: (i) liquid bismuth undergoes a structural rearrangement slightly above
melting (ii) liquid Bi exhibits a broad maximum in the sound velocity located
incidentally at the melting temperature.
