Complex magnetic phase diagram in Ce3Pd6Sb5 with a well-ordered superstructure

We report multiple magnetic phase transitions in single-crystalline Ce₃Pd6Sb₅ using magnetic, transport, and thermodynamic measurements. Ce₃Pd₆Sb₅ crystallizes in an orthorhombic structure (space group Pmmn), as a defect-induced variant of the well-known tetragonal CaBe₂Ge₂ structure. It undergoes two magnetic transitions: a second-order antiferromagnetic transition at TN1 = 6.6 K and a first-order one at TN2=5.8K. The hybridization between 4f electrons and conduction electrons is relatively weak in Ce₃Pd₆Sb₅, as revealed from the nearly full recovery of magnetic entropy Rln2 at TN1 and the low value of the electronic specific-heat coefficient of 30 mJ/(Ce-mol K2). We construct two field-temperature phase diagrams for magnetic fields applied parallel and perpendicular to the c axis, which, for H, shows multiple field-induced phases between TN1(H) and TN2(H), while Hall resistivity measurements point to the absence of a topological Hall effect.