Superconductivity Discovered in Neptunium Compound for the First Time

We grew a novel compound of NpPd5Al2 single crystal and discovered the world’s first superconductivity of the neptunium compound. The superconducting transition temperature is 5 K, which is relatively high among the heavy fermion superconductors.

The upper critical field where the superconductivity state is killed is a very large value of 15T, which is 500,000 times larger than the earth magnetism. Although the neptunium ion possesses the magnetism, the superconductivity emerges. Furthermore it is found that the unconventional superconductivity with anisotropic energy gap is realized.

The results were reported in the top page of "Kahoku Shimpo" on May 26 , and "Nikkan Kogyo Shimbun" and "Joyo Shimbun" on May 28. The paper, which was selected as one of the "Papers of Editor’s Choice", was published in "Journal of the Physical Society of Japan".

This work has been done in collaboration with Japan Atomic Energy Agency and Osaka University.