Researchers from Oxford, Stanford and the Lawrence Berkeley National Laboratory discovered a new 3D material (Na3Bi) that behaves like graphene. While it is very unstable, this is still a significant discovery as it shows that it's possible to find 3D materials that have similar properties to graphene.
The fact that graphene is a single sheet of atoms (a 2D material) makes it difficult to work with. A 3D material will be easier to handle, and this is why the researchers are excited about their discovery. The new material, a sodium-bismuth compound, is a three-dimensional topological Dirac semimetal - that has a unique behavior of its electrons (it's actually represents a new quantum state of matter).
This specific material has been actually produced a long time ago, but only now we have the powerful tools required to measure its electronic structure. The researchers are now looking for more stable compounds that behave similarly.