  Gold deposited on the Fe$_3$O$_4$(001) surface at room temperature was
studied using Scanning Tunneling Microscopy (STM) and X-ray photoelectron
spectroscopy (XPS). This surface forms a ($\sqrt2 \times \sqrt2$)R45$^{\circ}$
reconstruction, where pairs of Fe and neighboring O ions are slightly displaced
laterally producing undulating rows with `narrow' and `wide' hollow sites. At
low coverages, single Au adatoms adsorb exclusively at the narrow sites, with
no significant sintering up to annealing temperatures of 400 $^{\circ}$C. We
propose the strong site preference to be related to charge and orbital ordering
within the first subsurface layer of Fe$_3$O$_4$(001)-($\sqrt2 \times
\sqrt2$)R45$^{\circ}$. Due to its high thermal stability, this could prove an
ideal model system for probing the chemical reactivity of single atomic
species.
