We present a study of angle-resolved quantum oscillations of electric and thermoelectric transport coefficients in semimetallic , which has the particularity of displaying a large magnetoresistance. The Fermi surface consists of two pairs of electronlike and holelike pockets of equal volumes in a “Russian doll” structure. The carrier density, Fermi energy, mobility, and the mean-free path of the system are quantified. An additional frequency is observed above a threshold field and attributed to the magnetic breakdown across two orbits. In contrast to all other dilute metals, the Nernst signal remains linear in the magnetic field even in the high-field () regime. Surprisingly, none of the pockets extend across the axis of the first Brillouin zone, making the system a three-dimensional metal with moderate anisotropy in Fermi velocity, yet a large anisotropy in the mean-free path.