Siclanic is a copper alloy (CuNiSi) which has been extensively used at JET, the world's largest and most successful fusion device, for the fabrication of critical components. An optimised heat treatment resulted in a precipitation hardened material that exhibits much higher yield strength and electrical resistivity than similar copper alloys (e.g. CuCrZr), at a relatively wide range of temperatures, down to the ones achieved using liquid nitrogen cooling (-196oC). Siclanic also demonstrated good mechanical formability, high thermal conductivity, as well as high adherence to vacuum deposited ceramic coatings. This material is of special interest for the design of future fusion plants. It could be a strong candidate for the primary pumps of the next-step fusion machine (ITER). An extensive experimental campaign was undertaken at Imperial College (IC), London, to quantify both the tensile and fracture behaviour of this material at temperatures of 25oC, -80oC and -196oC. The tests included heat treatments and were accompanied by relevant fractographic analyses using optical and Scanning Electron Microscopes (SEM).