An implantable electrode for electrical stimulation of a body, for example, being a component of an implantable medical electrical lead, is preferably in the form of a coiled conductor wire, wherein the wire is formed by a tantalum (Ta) core directly overlaid with a platinum-iridium (Pt—Ir) cladding. When a maximum thickness of the Pt—Ir cladding defines a cladded zone between an outer, exposed surface of the electrode and the Ta core, a surface of the Ta core encroaches into the cladded zone by no more than approximately 50 micro-inches. The tantalum core may be cold worked to improve surface quality or formed from a sintered and, preferably, grain stabilized tantalum.