  Superconductor-insulator-superconductor tunnel junctions have been fabricated
on MgB2 that display Josephson and quasiparticle currents. These junctions
exhibit a gap magnitude, Delta~2.5 meV, that is considerably smaller than the
BCS value, but which clearly and reproducibly closes near the bulk Tc. In
conjunction with fits of the conductance spectra, these results are interpreted
as direct evidence of two-band superconductivity.
