Hemikek IV was a Delta Quadrant planet rich in minerals needed to repair warp coils, where the traitor Michael Jonas arranged for the Kazon-Nistrim to ambush Voyager in 2372.
The planet figures in the second-season episode Investigations. Crewman Jonas, who has been passing information to Seska, sabotages Voyager's warp coils so that the ship will need verterium cortenide. Neelix identifies Hemikek IV as the nearest source, exactly as the Nistrim intend.
Meanwhile Tom Paris, who has apparently left the ship in disgrace, is taken by the Kazon. His departure is a ruse planned with Janeway and Tuvok, and aboard the Nistrim vessel he finds proof of Jonas's guilt and of the trap waiting at Hemikek.
Paris escapes and warns Voyager. Neelix confronts Jonas in engineering, and the traitor dies when he falls into a plasma stream. The ambush fails.