  We present calculation of photoexcitation and high-harmonic generation in
bulk diamond induced by intense near-infrared laser pulse of photon energy 1.55
eV, time duration of 15 fs and peak field strength $F=$ 0.4 V/{\AA}. Depending
on the laser polarization direction, the pulsed irradiation creates
electron-hole pairs and transient density fluctuations in a localized region of
the crystal momentum space. As a consequence energetic inter- and intra-band
harmonics are generated with alternating phase during each half-cycle of the
driving pulse. The corresponding inter- and intra-band currents are in definite
phase relation with the laser pulse, reflecting the build-up of coherent
superposition of population between valence and conduction bands, and the
accelerated motion of charge carriers in their respective bands.
