  We report the discovery of strong photospheric resonance lines of Ga III, Ge
IV, Sn IV and Pb IV in the UV spectra of more than two dozen sdB and sdOB stars
at temperatures ranging from 22000 K to 40000 K. Lines of other heavy elements
are also detected, however in these cases more atomic data are needed. Based on
these discoveries, we present a hypothesis to explain the apparent lack of
silicon in sdB stars hotter than ~32000 K. The existence of triply ionised Ge,
Sn, and Pb suggests that rather than silicon sinking deep into the photosphere,
it is removed from the star in a fractionated stellar wind. This hypothesis
provides a challenge to diffusion models of sdB stars.
