[Durus]

A sheet of graphene has three dimensions, and while it's thickness (or depth) is only a single atom it is still a thickness or depth. If we could develop a sheet of some material made of some sort of sub atomic particle that had only the thickness of said single subatomic particle it would still be have three dimensions. Describing graphene as a two dimensional material is not only incorrect it ignores the model of the physical universe in which all known matter exists.

Being able to have a material with the characteristics of graphene but can be thicker than graphene is exciting. It still doesn't make one of the dimensions of graphene not exist.

[Svartalfiar]

Yes, GRAPHENE physically has 3 dimensions.

The electrical USE of graphene has 2 dimensions.

No matter what you do, electrons only move within the graphene lattice in two directions. I’m not describing graphene as a 2-dimensional structure, I am describing its use in 2 dimensions, because electrons can’t move in that third dimension to do anything useful. When you start layering graphene in order to gain that third dimension electrically, you lose the special properties that make the single layer so useful electrically. Different orientations lose effectiveness at different rates, but you end up with pencil lead. Which, as we know, is not very conductive. (I’m not confusing you by calling it ‘lead’, am I?) But what makes sodium bismuthide so special is it has that third dimension (electrically) that maintains those special properties despite having multiple layers.

Imagine you have a pile of 2x2 flat-top lego blocks. You can place them on a base sheet, but you can’t stack them on top of each other. Yes, each lego block has 3 sides, but your constructed piece can only be built and added on to in 2 dimensions.