Search for New Superconductors in RE-Si and Al-B Systems: a High Pressure High Temperature Approach*

We have searched for the presence of superconductivity in the RE-Si and Al-B systems using HP-HT synthesis. The RE-Si system has some of the common features that are present in high TC superconducting materials. We have synthesized Ce, Pr, Nd and Gd silicides undoped and doped with C and B. On the other hand, AlB$_{2}$ has some similarities with the superconducting MgB$_{2}$. We have tried to synthesize AlB$_{2}$ way off stoichiometry using HP-HT and thin films Phase Spread Alloy. The Al$_{0.67}$ B$_{2}$ would be the MgB$_{2}$ equivalent and good reason to expect superconductivity. We discuss the results for both systems after a careful analysis of several physical properties (SQUID, Modulated Microwave Absorption) and x-ray powder diffraction.