A good candidate for superconductors is fullerenes. However, these molecules are quite expensive. But there is a more affordable and interesting option - shungite, because there are fullerene molecules in shungite carbon.
https://shungite-c60.com/fullerenes-in-shungite-stone/
By the way, shungite is an excellent conductor at room temperature. Perhaps, under some special conditions in the future, it will be possible to use it and detect superconductivity at room temperature. In the meantime, it becomes a superconductor precisely when the temperature rises, which may be and will be better.