  Point-contact spectroscopy measurements on magnesium diboride reveal the
existence of two superconducting energy gaps closing at the same transition
temperature in line with the multiband model of superconductivity. The sizes of
the two gaps ($\Delta_{\pi}$ = 2.8 meV and $\Delta_{\sigma}$ = 6.5-7 meV) are
respectively smaller and larger than the expected weak coupling value of the
one-gap superconductor. The smaller gap is rapidly filled by a small magnetic
field of about 1-2 Tesla much lower than the real upper critical field
$H_{c2}$. The larger gap is closed at the anisotropic $H_{c2}$. Above the gap
energies reproducible non-linearities are observed at the characteristic phonon
energies of MgB$_2$.
