Imaging of the Fermi Surface of $1T$-${\mathrm{Ta}}_{0.9}$${\mathrm{Hf}}_{0.1}$${\mathrm{S}}_2$ by X-Ray Diffuse Scattering

Using x-ray diffuse scattering, we have observed enhanced Kohn anomalies in the two-dimensional conductor ${\mathrm{Ta}}_{0.9}$ ${\mathrm{Hf}}_{0.1}$ ${\mathrm{S}}_2$. From this, we have deduced the shape of the Fermi surface of this compound throughout a wide region of reciprocal space. The results in the ($h0l$) planes demonstrate the two-dimensionality of the electronic states in this substance. The results in the layers $h$, $k$, $\pm \frac{1}{3}$ prove that the topographic shape originally postulated by Williams, Parry, and Scruby is correct.