High‐Pressure Synthesis of Samarium Hydrides

We report an experimental study on the high‐pressure syntheses and characterizations of the samarium (Sm) hydrides system, for which the theoretical predictions have long struggled to accurately describe the crystal structures and superconducting properties. By laser heating Sm and ammonia borane (BH 3 NH 3 ) compressed in diamond anvil cells (DACs), we successfully synthesized a series of Sm hydrides, including P 6 3 / mmc SmH 9 , Im ‐3 m SmH 6 , I 4/ mmm SmH 4 , Pm ‐3 n SmH 3 , P 6/ mmm SmH 2 , and Fm ‐3 m SmH 2‐x . Electrical transport measurements performed in four independent experimental runs revealed metallic behavior without any signature of superconductivity, while some samples exhibited anomalies suggestive of magnetic or electronic transitions. These findings establish Sm hydrides as a model platform for probing the interplay between strong electronic correlations, magnetism, and superconductivity in high‐pressure hydrides, highlighting the complex role of 4 f electrons in governing their physical properties.