On the absence of spin-splitting in alpha-(BEDT-TTF)2KHg(SCN)4

We report the results of a detailed study of the field orientation-dependence of the de Haas-van Alphen waveform in $\alpha$-(BEDT-TTF)$_2$KHg(SCN)$_4$. By considering the field orientation-dependence of the sign and phase of the fundamental $\alpha$ frequency, at fields both well above and below the kink transition field, it is found that a single value for the product of the effective mass with the electron {\it g}-factor can explain the experimental data deep within both the high magnetic field and low magnetic field phases. This implies that spin-splitting does not occur within the low magnetic field phase until the angle between the magnetic field and the normal to the conducting planes is $\sim$~42$^\circ$. This finding contrasts greatly with that recently published by Sasaki and Fukase, implying that electron-electron interactions do not play a significant role in the formation of the charge-density wave ground state. The manner in which the amplitude of the waveform of the oscillations is damped within the low magnetic field phase is indicative of a non harmonically indexed reduction of the amplitude, thereby eliminating both magnetic breakdown and impurity scattering as dominant damping mechanisms within this phase. Meanwhile, the presence of a large amplitude second harmonic within the low magnetic field phase that has a negative sign over a broad range of angles can only be explained by the frequency doubling effect.