Seprom is best obtained by refining Promerium in the Skylab, at the rate of 189 sperom per hour(at max. upgraded modules). Considering it is much more valuable than Promerium due to it further increasing the performance of shield generators (40% increase) or boost the firepower of rockets or lasers (60% increase).
Seprom is one of three ores that cannot be sold, along with Xenomit and Palladium. Seprom is also required in the Skill Tree when upgrading classes 2 and 3, as well as required in Tech Center to create certain upgrades.