Tetraburnium
Tetraburnium was a metallic alloy capable of withstanding extreme amounts of  and pressure. 

In 2375, at Seven of Nine's suggestion, the  was constructed of tetraburnium alloys, allowing it to enter the atmosphere of a class 6 gas giant and retrieve a multi-spatial probe. A Malon shuttlecraft, built for the same purpose, also had a tetraburnium hull. ()

See also 
 Diburnium
 Triburnium

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Materials