Biological scaffolds are used for the synthesis of inorganic materials due to their ability to self-assemble and nucleate crystal formation. We report the self-assembly of engineered M13 bacteriophage as a template for Co-pt crystals. A M13 phage library with an octapeptide library on the major coat protein (pVIII) was used for selection of binders to cobalt ions. Fibrous structures with directionally ordered M13 phage were obtained by interaction with cobalt ions. Co-Pt alloys were synthesized on the fibrous scaffold, and their magnetic properties were characterized. The mineralization showed organized nanoparticles on fibrous bundles. This approach using the phage pVIII library allows for genetic selection that both induces assembly of the phage and directs mineralization of the selected inorganic material.