  We present ASCA GIS observations (total exposure 100-200 ksec) of three
fields which form part of our deep ROSAT survey. We detect 26 sources down to a
limiting flux (2-10 keV) of 5x10^{-14} erg cm-2 s-1. Sources down to this flux
level contribute 30 per cent of the 2-10 keV X-ray background. The number-count
distribution, logN-logS, is a factor of three above the ROSAT counts, assuming
a photon spectral index of 2 for the ROSAT sources. This suggests the presence
at hard energies of a population other than the broad-line AGN which contribute
to the ROSAT counts. This is supported by spectroscopic observations that show
a large fraction of sources that are not obvious broad-line AGN. The average
1-10 keV spectral index of these sources is flat (0.92+-0.16), significantly
different than that of the broad-line AGN (1.78+-0.16). Although some of the
Narrow Emission Line Galaxies which are detected with ROSAT are also detected
here, the nature of the flat spectrum sources remains as yet unclear.
