Nanostructures of Ag and Au, as well as their composites both in alloy and core-shell forms, have been conventionally studied as a tunable optical platform for surface enhanced Raman spectroscopy. We were able to prepare Au-Ag particles with an unconventional structure where both metals are configured to maximize interfacial area. Here, Ag nanoparticles of ~1 nm diameter are dispersed inside a matrix of Au. In particular, these materials show unusual transitions to a highly conductive, strongly diamagnetic state at ambient temperatures and pressures. Further, in their optical properties, a suppression of Mie-like behaviour is observed along with the emergence of a broad, surprisingly nondissipative, scattering resonance. The collapse of electrical resistance to immeasurably small values occurs when samples are cooled below temperatures as high as 320 K, at ambient pressure. In some cases, this state persists even to 400 K. Preliminary non-equilibrium transport, inductive response and magnetotransport data indicate a strong similarity to transitions to a superconducting state. The first half of the presentation will provide an overview of material properties, including results from structural, optical, magnetic and earlier electrical measurements. The second part will describe more recent electrical measurements and experimental details.