I have a pictorial example in a book here of a solid that behaves very strangely indeed. I would have called it 'biaxial metallicity' but I have no idea what the correct term is - the material is apparently metallic in one direction but not in another - that is, appears to obey the free or nearly-free electron model only in one direction. It's described as 'KCP' and given the formulation (K2(Pt(CN)4Br0.3).3H2O). I haven't been able to find this anywhere else. Anyone have any idea what this stuff is and have any more sources for information? Oops, I should have mentioned the book. It's Elliot, The Physics and Chemistry of Solids.