This thesis presents an experimental study of compounds in which the physics is dominated by the f-electrons. Whilst united by their electronic configuration, these compounds highlight the diversity associated with such systems. CeOs4Sb12 undergoes a valence transition where the behaviour of the 4f electron transforms from quasi-localised to itinerant. Here, the temperature-field phase diagram is constructed from resistivity, magnetostriction, and MHz conductivity (PDO) measurements and the phase boundary is found to differ markedly from the textbook elliptical behaviour expected for valence transitions in two distinct regions. In one region, this deviation is likely due to the proximity of CeOs4Sb12 to a strain-induced topological semimetal phase. In the other, quantum-oscillation measurements suggest that quantum fluctuations associated with a quantum critical point may be responsible. Whilst IrO2 and OsO2 are of interest in their own right, they are also common impurities formed in the growth of many Ir- and Os-based compounds, which include many f-electron systems of current research interest. In both of these contexts, an accurate knowledge of the Fermi surface is desirable. Using torque magnetometry, an angle- and temperature-dependent survey of the quantum-oscillation spectrum at higher fields and lower temperatures than previously studied reveals new information regarding quasiparticle effective masses as well as key differences in the Fermi surface of OsO2 compared to previously reported results. In Ho2Ir2O7, the Ho3+ ions posses a large magnetic moment (_ 10 _B) provided by the 4f electrons. Here, measurements of the magnetisation and resistivity, in combination with dipolar Monte Carlo simulations, show an intriguing interplay between the spin-ice physics of the strongly frustrated Ho3+ moments and the magnetically ordered Ir4+ ions. Specifically, the Ho{Ir interaction plastically deforms the Ir domains under an applied magnetic field. The precise control of antiferromagnetic domains is a key goal in the development of next-generation spintronics devices; this result provides a set of ingredients for how this may be achieved using applied magnetic fields. Furthermore, these measurements show the magnetoresistance to be highly sensitive to the density of monopoles, in a way that holds promise to develop an experimental indicator of the latter.