  As devices are reduced in size, interfaces start to dominate electrical
transport making it essential to be able to describe reliably how they transmit
and reflect electrons. For a number of nearly perfectly lattice-matched
materials, we calculate from first-principles the dependence of the interface
transparency on the crystal orientation. Quite remarkably, the largest
anisotropy is predicted for interfaces between the prototype free-electron
materials silver and aluminium for which a massive factor of two difference
between (111) and (001) interfaces is found.
