  The typical accreting neutron star, Aquila X-1, was observed with Suzaku
seven times in the decay phase of an outburst in 2007 September-October. Among
them, the second to the fourth observations were performed 10 to 22 days after
the outburst peak, when the source was in the hard state with a luminosity of
2x10^36 erg/sec. A unified spectral model for this type of objects
approximately reproduced the 0.8--100~keV spectra obtained in these 3
observations. However, the spectra all exhibited an enigmatic hump-like excess
around 30 keV, above the hard X-ray continuum which is interpreted as arising
via Comptonization. The excess feature was confirmed to be significant against
statistical and systematic uncertainties. It was successfully represented by a
Gaussian centered at ~32 keV, with a width (sigma) of ~6 keV and an equivalent
width of ~8.6 keV. Alternatively, the feature can also be explained by a
recombination edge model, that produces a quasi-continuum above an edge energy
of ~27 keV with an electron temperature of ~11 keV and an equivalent width of
~6.3 keV. These results are discussed in the context of atomic features of
heavy elements synthesized via rapid-proton capture process during
thermonuclear flashes.
