  Edelmann (2003) identified two chemically peculiar hot subdwarfs, PG 0909+276
and UVO 0512-08, as having very high overabundances of iron-group elements. We
obtained high-resolution ultraviolet spectroscopy in order to measure
abundances of species not observable in the optical, and to seek evidence for
chemical stratification in the photosphere. Abundances were measured in three
wavelength regions; the optical 3900\AA-6900\AA\ range was re-analysed to
confirm consistency with Edelmann. Ultraviolet spectra were obtained with the
Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope
(HST), covering the far-UV (1140\AA-1740\AA) and the near-UV (1740\AA-2500\AA).
We computed a grid of theoretical LTE spectra to find basic parameters
(effective temperatures, surface gravity, surface hydrogen and helium
fractions). We measured abundances using a spectral-synthesis approach in each
wavelength range. We confirm that several iron-group metals are highly
enriched, including cobalt, copper and zinc, relative to typical sdB stars. We
detect gallium, germanium, tin, and lead, similar to analysis of ultraviolet
spectra of some other sdB stars. Our results confirm that PG 0909+276 and UVO
0512-08 exhibit peculiarities which make them distinct from both the normal
H-rich sdB and intermediate He-rich sdB stars. The process which leads to this
particular composition has still to be identified.
