Structural and electronic properties of single-crystal Fe$_{1-x}$Co$_{x}$As

Shortly after the discovery of the iron pnictide superconductors, it was found that cobalt substitution on the iron site in the 122 ternary systems AEFe$_{2}$As$_{2}$ (AE = alkali earth) suppresses the magnetic order of the parent compounds and induces superconductivity. While transition metal substitution in the intermetallic iron arsenide superconductors is one of the most studied aspects of these materials, there is little known about the effects of substitution on the related binary system FeAs. We present transport and magnetization measurements performed on single crystals of the cobalt-substituted system Fe$_{1-x}$Co$_{x}$As, and discuss the evolution of the phase diagram of this system.