  We study the phase matching of resonant high-harmonic generation (HHG) and
high-order frequency mixing (HFM) in plasma. We solve numerically the
propagation equations coupled with the time-dependent Schr\"odinger equation
for the nonlinear polarisation. The macroscopic harmonic signal is enhanced in
the vicinity of a multiphoton resonance with the transition between the ground
and autoionising states of the generating ion. We show that narrow and strong
resonances (as for gallium and indium ions) provide compensation of the plasma
dispersion in a spectral region above the exact resonance improving the phase
matching and leading to a high macroscopic signal. The compensation does not
take place for a wider resonance (as for manganese ions), instead the phase
matching is achieved in the HFM process. Comparing the XUV generated in
manganese plasma and in neon gas, we show that the resonant HHG in plasma is an
order of magnitude more effective than in the gas, moreover another order of
magnitude can be gained from the propagation using HFM in plasma.
