Contact-less measurements of Shubnikov-de Haas oscillations in the magnetically ordered state of CeAgSb${}_2$ and SmAgSb${}_2$ single crystals

Shubnikov - de Haas oscillations were measured in single crystals of highly metallic antiferromagnetic SmAgSb${}_2$ and ferromagnetic CeAgSb${}_2$ using a tunnel diode resonator. Resistivity oscillations as a function of applied magnetic field were observed via measurements of skin depth variation. The effective resolution of $\mathrm{\Delta }\rho \simeq 20$ p$\mathrm{\Omega }$ allows a detailed study of the SdH spectra as a function of temperature. The effects of the Sm long - range magnetic ordering as well as its electronic structure ($4f$-electrons) on the Fermi surface topology is discussed.