Search for new superconductors in the La-Si-C system*

We have searched for the presence of superconductivity in the La-Si-C system in bulk and thin film samples. This system has some of the common features that are present in high T$_{C}$ superconducting materials. It is a multi-element compound and also incorporates a light element, Carbon. Furthermore, one of the binary phases, La$_{5}$Si$_{3}$ exhibits a tetragonal layered structure. This system exhibits the presence of a possible new superconducting compound with T$_{C}$'s ranging from 6.1 K to 8.5 K. In the binary La-Si system there are five inter-metallic phases. Among these phases, those that exhibit superconductivity are: LaSi$_{2}$ with T$_{C}$ of 2.3 K, La$_{3}$Si$_{2}$ with a T$_{C}$ of 2.1 K and La$_{5}$Si$_{3}$ with a T$_{C}$ of 1.6 K. A careful analysis of several physical properties (SQUID, Modulated Microwave Absorption) and x-ray powder diffraction, (using Rietveld refinement) shows that superconductivity in this system could be ascribed to intermediate binary (La$_{2}$C$_{3})$ and single (La-\textit{$\beta $}) phases of the system.