A samarium/cobalt alloy could be used in magnets that were much better although heavier than neodymium magnets. This made them useful in the medical field.
(Note: The background section of this page uses most of the same words as Terra Futura's page on rare earth elements to save time.)
China was the biggest producer one of the most common rare earth elements: Neodymium. Neodymium was found in magnets which also contained iron. During the early 21st century, China started regulating the exportation of neodymium. This threatened the economies of the world. An American company called Molycorp opened its own neodymium mine in the United States. This took a bite out of China's near-monopoly. Meanwhile, scientists started making magnets that had less neodymium in them but still worked. Of course, neodymium and other rare earths would play an important role in fishing: Shark Repellant.
A scientist named Patrick Rice discovered while repairing a tank that sharks were allergic to neodymium magnets. This got him interested and he wondered if sharks could be saved from fish hooks. There was one problem. Fish hooks were made of magnetic metals. Rice searched for a solution. It turned out that all rare earth elements were capable of repelling sharks by creating a small electric shark. The most common in use was samarium. It electrocuted sharks out of the way, but other fish were not put off by that. This saved sharks from fish hooks. Samarium was also incorporated into diving suits to keep sharks away when they not being studied. This was not the only application of samarium. When alloyed with cobalt, samarium made a supermagnet that could be used for medicine.
Tech Level: 10
Scientist Brad Nelson was the inventor of a micro-robot or nanocar that could treat a form of blindness caused by blocked blood vessels in the retina. Using a samarium/cobalt alloy, Nelson invented a nanocar that revolutionized the way blindness was treated in the retina. It could be controlled by magnetic fields allowing a doctor to direct the nanocar to the retina. Brad Nelson, of course, sought to look beyond that to a nanocar that swam in blood vessels. At a very small size, however, the water molecules would become a big drag. Brad Nelson took advantage of a feature of bacteria. The tail or flagellum of a bacterium turned like a corkscrew. This allowed Nelson to create smaller robots that even repair DNA. This revolutionized medicine in general.