  Despite more than half a century of studies in heavy-fermion compounds, a
full understanding of the various possible magnetic ordering phenomena is still
far from complete. Some heavy-fermion materials show so-called hidden-order
phases, which are invisible to conventional diffraction techniques. The
multipolar moments of the $f$-electrons in their specific crystal field
environment play a decisive role in the formation of these phases. Such
hidden-order phases have been observed in a variety of compounds containing
$4f$ and $5f$ elements, like URu$_2$Si$_2$, NpO$_2$, YbRu$_2$Ge$_2$, and
CeB$_6$. The competition or coexistence of multipolar ordering with more
conventional magnetic order parameters, such as ferro- or antiferromagnetism,
gives rise to complex magnetic-field$-$temperature phase diagrams in these
compounds that provide a rich playground for experimental and theoretical
investigations. Here I examine the pure and La-doped $f$-electron system
CeB$_6$, as well as Ce$_{3}$Pd$_{20}$Si$_{6}$, by means of neutron scattering.
The magnetic field dependence of the zone center exciton mode in CeB$_6$ was
studied in fields up to 14.5 T and compared with the existing theory. A long
standing question of the applicability of the phenomenological temperature
dependence $\Gamma=k_{\text B}T_{\text K}+A \sqrt{T}$, where $T_{\text K}$ is
the Kondo temperature, for two limiting cases, the Kondo lattice and Kondo
impurity, has been investigated on a set of samples diluted with lanthanum. In
Ce$_{3}$Pd$_{20}$Si$_{6}$, the order parameter of the AFQ phase was uncovered,
and its field dependence was studied in fields up to 9 T.
