  In this article we characterize the macroscopic electromagnetic response of a
nested wire metamaterial with a high degree of bulk structural asymmetry. The
unit cell of the considered metamaterial contains two sets of metallic wires,
one set consisting of an array of straight wires and another formed by a
racemic array of helical-shaped wires. We study the scattering of
electromagnetic waves in a metamaterial slab and show that the electromagnetic
coupling between both arrays of wires can originate Fano resonances with narrow
lineshape. The origin of the resonances is rooted in the formation of a
sub-radiant mode in the metamaterial wherein the net polarization vector
vanishes. We envision that the proposed configuration, with sharp resonances
whose quality factor can be greatly enhanced by tuning the structural
parameters of the wires, may have promising applications in sensing and
switching in a broad frequency range from the microwave regime up to THz
frequencies.
