The non-retarded dispersive force between an electrically polarizable atom and a magnetically polarizable one

Using perturbative QED we show that, while the retarded dispersive force between an electrically polarizable atom and a magnetically polarizable one is proportional to $1\mathrm{/}{r}^8$, where $r$ is the distance between the atoms, the non-retarded force is proportiaonal to $1\mathrm{/}{r}^5$. This is a rather surprising result that should be compared with the dispersive van der Waals force between two electrically polarizable atoms, where the retarded force is also proportional to $1\mathrm{/}{r}^8$, but the non-retarded force is proportional to $1\mathrm{/}{r}^7$.