I enjoy hearing about these "happy accidents" in Physics. This one may have lots of interesting potential.
Diamagnatism has been a well known phenomenon in Hightly Ordered Pyrolytic Graphite (HOPG). In fact, HOPG is produced in a similar way as their experiment here was doing. Instead they produced something which is ferromagnetic, and has properties similar to steel, except made from pure carbon.
This material can also be converted to a semi-conductor, and maybe it can be used for solid state electronics. Possibly for solar panels. It is also really hard - harder than steel, but not as hard as diamond.