Both components of the composite-spectrum binary o Leo have Am characteristics, even though the primary is an evolving giant ($\log g=3.25$) with $T_{\rm eff} \sim 6100\,{\rm K}$. This is believed to be the first isolation of such a cool Am star. The finding challenges the theories of diffusion which are widely accepted as the cause of metallicism. The primary component (o Leo A) appears to be deficient in Ca and Sc, as are classical Am stars. Its unusual state may be attributable either to its current state of rapid evolution, or to regular Am-star evolution that is difficult to recognize spectroscopically. A full account of this research appeared in AJ 123, 988-1001, 2002.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html
