Samarium Hexaboride Crystal Blurs Metal-Insulator Line, "[no] remotely credible hypothesis proposed at this moment in time"

The paper itself is here: http://science.sciencemag.org/content/early/2015/07/01/science.aaa7974

Insulators occur in more than one guise; a recent finding was the class of topological insulators, which host a conducting surface juxtaposed with an insulating bulk. Here we report the observation of an unusual insulating state with an electrically insulating bulk that simultaneously yields bulk quantum oscillations with characteristics of an unconventional Fermi liquid.

[removed]