  The thermal expansion of polycrystalline MgB2 from 5-300 K is studied using
high-resolution capacitance dilatometry. The thermal expansivity exhibits a
small jump of -5.8x10-8 K-1 at Tc (in accord with expectations from the
Ehrenfest relationship and published specific heat and pressure data) and a
negative peak-like feature close to 5 K. No indications of any structural
instabilities are observed.
