  The model of two (s and p) channel superconductivity known to be necessary to
explain the superconductivity in MgB2 has been applied to the Al1-xMgxB2
diborides by tuning x from MgB2 to AlMgB4. The evolution of the interband
coupling parameter (probing the strength of the interchannel pairing due to
quantum interference effects) and the two gaps in the s and p channel as a
function of x have been calculated. While in MgB2 the quantum interference
effects give an amplification of Tc by a factor of 1.5 in comparison with the
dominant intra s band single channel pairing, in AlMgB4 the amplification is
about 100, in comparison with the dominant intra p band single channel pairing.
