ThMoIrSiC: An Intergrown Superconductor by Structure Design.

Exploration of new superconductors in multicomponent complex systems remains challenging. Among complex superconductors, those containing distinct superconducting layers are quite rare. In this work, based on the block-layer model together with formation energy calculations, we have designed and successfully synthesized a quinary intermetallic compound, ThMoIrSiC. The new material crystallizes in an intergrowth structure with an alternate stacking of superconducting ThMoSiC and ThIrSi block layers along the crystallographic axis. The interblock-layer interaction is dominated by the Si-Ir bonding, which results in a relatively shorter interlayer distance and a stronger coupling between [MoSiC] and fluorite-type [SiIr] layers. Enhanced superconductivity, with a superconducting transition temperature of = 3.4 K and a zero-temperature upper critical field of (0) = 9.5 kOe, is revealed by measurements of electrical resistivity, magnetic susceptibility, and specific heat. The strategy of the block-layer design demonstrated here can be extended to other intergrowth systems with various functional motifs.