## 2 Methods  
First, ab initio calculations of optical permittivity have been performed for different transition metals (Cr, W, Ti, Fe, Au, and Ni) at different electron temperatures up to 30,000 K using Abinit software [25]. The electronic structure (density of states, band filling, electron distribution) were calculated using a finite-temperature density functional theory with appropriate exchange-correlation functionals (GGA for Cr, W, Ti, Fe, and Ni and LDA for Au) and projector-augmented wave atomic data to consider nuclei and core electrons effects. The finite electronic temperature \(T_{e}\) is taken into account by considering a Fermi-Dirac distribution function applied to the Kohn-Sham eigenstates, thus describing a \(T_{e}\)-dependent electronic structure as a result of self-consistent calculation. The quantum molecular dynamic simulation was performed at an ionic temperature of 300 K to account for electron-phonon interaction in optical properties. Then we used a Kubo-Greenwood formalism to describe the possible electronic transitions and Kramers-Kronig relation to finally calculate the permittivity. The high electron temperature is considered to reproduce the transient distribution of photoexcited electrons at the laser pulse fluences used for nanostructuring. A detailed description of these calculations can be found in our previous work [24] with some additional information for Au in Ref. [5]. Then, the Drude-Lorentz model was fitted to the ab initio permittivity with the aim of providing a simple and convenient way to interpret and apply the calculated data. The Drude-Lorentz model is often used for the parametrization of optical constants of metals [20] with the complex permittivity dispersion describing the free electrons (intraband transitions) and bound electrons (interband transitions):  
\[\epsilon(\omega)=\epsilon(\omega)^{(f)}+\epsilon(\omega)^{(b)}. \tag{1}\]  
The intraband contribution \(\epsilon(\omega)^{(f)}\) is described by the free-electron Drude model:  
\[\epsilon(\omega)^{(f)}=1-\frac{f_{0}\omega_{p}^{2}}{\omega^{(}\omega-i\Gamma_ {0})}, \tag{2}\]  
where \(\omega_{p}\) is the plasma frequency, \(f_{0}\) is the free-electron oscillator strength, and \(\Gamma_{0}\) is the damping constant related to the electron collision frequency. The interband contribution \(\epsilon(\omega)^{(b)}\) follows the [PERSON] model:  
\[\epsilon(\omega)^{(b)}=\sum_{j=1}^{k}\frac{f_{j}\omega_{p}^{2}}{\omega_{j}^{2 }-\omega^{2}-i\omega\Gamma_{j}}, \tag{3}\]  
which describes \(k\) interband transitions with frequency \(\omega_{j}\), oscillator strength \(f_{j}\), and lifetime \(1/\Gamma_{j}\). To fit the Drude-Lorentz model to the ab initio data, the Basin-hopping optimization method was used. The Basin-hopping algorithm was designed to mimic the energy minimization of clusters of atoms and thus is suitable for our case where the Drude-Lorentz oscillators have similar energy landscapes [26]. The difference between the model and the data was minimized based on the objective function \(\chi^{2}\):  
\[\chi^{2}=\sum_{i=1}^{N}\left[\left|\frac{\epsilon_{1}(\omega_{i})-\epsilon_{1} ^{data}(\omega_{i})}{\epsilon_{1}^{data}(\omega_{i})}\right|+\left|\frac{ \epsilon_{2}(\omega_{i})-\epsilon_{2}^{data}(\omega_{i})}{\epsilon_{2}^{data} (\omega_{i})}\right|\right]^{2}, \tag{4}\]  
where the sum runs over all \(N\) data points, and \(\epsilon_{1}\) and \(\epsilon_{2}\) are the real and imaginary parts of the permittivity \(\epsilon=e_{1}+i\epsilon_{2}\). Note that the relative permittivity is considered everywhere. A reduced objective function \(\chi_{r}^{2}=\chi^{2}/N\) was also calculated and presented below. A value of \(\chi_{r}^{2}\) less than unity is expected for a good fit. A Python code implementing the data fitting is provided in the Supplementary Materials. During the optimization procedure, we fixed \(k=4\) in Equation (3). The preliminary analysis showed that such a number of interband terms was sufficient for all considered metals and electron temperatures.