## 2 Materials and Methods
The dispersion relation of SPPs at a planar interface between the dielectric medium and metal forming a simple plasmonic structure in the complex conductivity and frequency domain is written as [20]:  
\[k_{sp}(\sigma,\,\omega)=\frac{2\pi}{\lambda}\sqrt{\frac{\varepsilon_{r}( \sigma,\,\omega)\varepsilon_{d}}{\varepsilon_{r}(\sigma,\,\omega)+ \varepsilon_{d}}} \tag{2}\]  
where \(\varepsilon_{d}\) is the permittivity of the host material. By making a step forward towards complex nanostructures, we made an assumption that the wavelength and the electromagnetic field penetration depth in the material are much larger that the size of inclusions suspended in a dielectric matrix. It is worthwhile mentioning that effective Maxwell Garnett model can be employed aiming to characterize the optical properties of the nanocomposite under consideration. The former approach is possible, if the interference effects of the inclusions are neglected and their volume fraction is as small as \(1/3\). Thus, one may apply the homogenization procedure and the effective complex permittivity of the nanocomposite can be expressed as follows  
\[\varepsilon_{nc}(\sigma,\,\omega)=\varepsilon_{n}\bigg{[}1+\frac{f}{(1-f)/3+ \varepsilon_{n}/(\varepsilon_{m}(\sigma,\,\omega)-\varepsilon_{n})}\bigg{]} \tag{3}\]  
where \(\varepsilon_{n}\) is the permittivity of the host material of the nanocomposite and \(f\) is the number of nanoparticles in the matrix. Based on the effective medium approximation one may calculate the effective permittivities of the anisotropic nanowire metamaterial (hypercrystal) according to [21]:  
\[\varepsilon_{\perp}(\sigma,\,\omega)=\varepsilon_{d}\bigg{[}\frac{\varepsilon _{m}(\sigma,\,\omega)(1+\rho)+\varepsilon_{d}(1-\rho)}{\varepsilon_{m}(\sigma, \,\omega)(1-\rho)+\varepsilon_{d}(1+\rho)}\bigg{]} \tag{4}\]  
\[\varepsilon_{||}(\sigma,\,\omega)=\varepsilon_{m}(\sigma,\,\omega)\rho+ \varepsilon_{d}(1-\rho) \tag{5}\]  
Figure 1: Schematic system under consideration, involving a semi-infinite hypercrystal (\(x>0\)) and a nanocomposite with semiconductor inclusions (\(x<0\)) (**a**) and metamaterial (hypercrystal) unit cell (**b**). where \(\varepsilon_{\rm d}\) is the permittivity of the host material, \(\varepsilon_{\rm m}\) is the permittivity of the inclusions embedded into the host material and \(\rho\) is the metal filling fraction ratio, which is calculated as:  
\[\rho=\frac{nanowire\ area}{unit\ cell\ area} \tag{6}\]  
The metal filling fraction (\(\rho\)) is calculated based on the values of the pore diameter (\(d\)) and spacing (\(S\)) (Figure 1b). By taking into account a perfect hexagonal structure, the equation [22; 23] is applied as follows:  
\[\rho=\frac{\pi d^{2}}{2\sqrt{3}S^{2}} \tag{7}\]  
Based on this assumption one may derive a dispersion relation for the surface modes propagating at the interface between two anisotropic media. It is of particular importance to obtain a single surface mode with the propagation constant [24] by calculating the tangential components of the electric and magnetic fields at the interface  
\[\beta(\sigma,\ \omega)=k\left(\frac{\left(\varepsilon_{||}(\sigma,\ \omega)- \varepsilon_{nc}(\sigma,\ \omega)\right)\varepsilon_{\perp}(\sigma,\ \omega)\varepsilon_{nc}(\sigma,\ \omega)}{\varepsilon_{\perp}(\sigma,\ \omega)\varepsilon_{||}(\sigma,\ \omega)- \varepsilon_{nc}^{2}(\sigma,\ \omega)}\right)^{1/2} \tag{8}\]  
By substituting (3)-(5) in (8), one may result in the dispersion relation as follows:  
\[