Why does samarium hexaboride conduct at room temperature but insulate when cooled?

[Robert Sanchez]

I'm no physicist, but I found this material to be interesting.

Samarium Hexaboride is a crystal that exhibits conductive properties at room temperature and insulating properties when cooled to below minus 223 degrees Celsius.

A layman's article...

https://www.quantamagazine.org/20150702-paradoxical-crystal-baffles-physicists/

 

[ZapperZ]

This is from 2015. There has been quite a few more work being done in this area of topological insulator since then.

Zz.