  We report an unusual anisotropic paramagnetic peak effect observed in
reversible magnetization of a single crystalline nodal superconductor
$\text{Rh}_{17}\text{S}_{15}$. Both temperature- and field-dependent
magnetization measurements reveal a distinct novel vortex state above
approximately 1 T. This peak effect is most pronounced when the magnetic field,
$H$, is applied parallel to the $\left[111\right]$ direction, whereas it
diminishes for $H\parallel\left[110\right]$. Intriguingly, for
$H\parallel\left[100\right]$, instead of a peak, we observe a step-like
decrease in $M(T)$, with the step amplitude increasing in larger applied
magnetic fields. This behavior is opposite to the expectations of conventional
Meissner expulsion. The magnitude of the peak effect, expressed in terms of
dimensionless volume susceptibility, is on the order of $\Delta\chi=10^{-5}$
(with full diamagnetic screening corresponding to $\chi=-1$). The observed
anisotropic paramagnetic vortex response is unusual considering the cubic
symmetry of $\text{Rh}_{17}\text{S}_{15}$. We propose that in this distinct
vortex phase, a small but finite attractive interaction between vortices below
$H_{c2}$ may be responsible for this unusual phenomenon. Furthermore, the
vortices seem to prefer aligning along the $\left[111\right]$ direction,
rotating toward it when the magnetic field is applied in other directions. Our
findings add another item to the list of unusual properties of
$\text{Rh}_{17}\text{S}_{15}$ that attracted recent attention as the first
unconventional superconductor that has a mineral analog, miassite, found in
nature.
