Quadratron

A quadratron was a type of subatomic particle.

Its' properties and likely even its' existence were unknown to humans during the 1970s, but Solar Terrarium humanoids were not only familiar with them, but they had quadratronic technology, such as their solar robot.

Properties
Nothing was revealed about the properties of a quadratron particle, other than it was capable of generating a wave of energy that was similar to magnetism.

It's name gives us a hint at what it could have been; the "quad" prefix of the word implies that the particle may have been a combination of four particles, but this is just conjecture based on the name, and even if that's true, it's impossible to know what four particles it takes to make a quadratron.