Yurium

Yurium (YU2) is a chemical compound of the element yttrium with two molecules of uranium.

History and specifics
This compound typically stored energy and could be used as an explosive. Trapped in a space anomaly, a freighter captain, one Bela Tyken, used anicium and yurium from his cargo bays to create a massive explosion. 

Jakmanite 632, a radioisotope, could be created artificially from the decay of high-energy yurium. 

In the year 2365, a sensor scan by the Federation starship USS Enterprise (NCC-1701-D) registered yurium comprising 2% of the atmosphere of the planet Theta VIII.