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Single crystal study of the layered heavy fermion compounds Ce$_2$PdIn$_8$, Ce$_3$PdIn$_{11}$, Ce$_2$PtIn$_8$ and Ce$_3$PtIn$_{11}$

We report on single crystal growth and crystallographic parameters results of Ce$_2$PdIn$_8$, Ce$_3$PdIn$_{11}$, Ce$_2$PtIn$_8$ and Ce$_3$PtIn$_{11}$. The Pt-systems Ce$_2$PtIn$_8$ and Ce$_3$PtIn$_{11}$ are synthesized for the first time. All these compounds are member of the Ce$_n$T$_m$In$_{3n+2m}$ (n = 1, 2,..; m = 1, 2,.. and T = transition metal) to which the extensively studied heavy fermion superconductor CeCoIn$_5$ belongs. Single crystals have been grown by In self-flux method. Differential scanning calorimetry studies were used to derive optimal growth conditions. Evidently, the maximum growth conditions for these materials should not exceed 750 $^{\circ}$C. Single crystal x-ray data show that Ce$_2$TIn$_8$ compounds crystallize in the tetragonal Ho$_2$CoGa$_8$ phase (space group P4/mmm) with lattice parameters a =4.6898(3) $Å$ and c =12.1490(8) $Å$ for the Pt-based one (Pd: a = 4.6881(4) $Å$ and c = 12.2031(8) Å). The Ce$_3$TIn$_{11}$ compounds adopt the Ce$_3$PdIn$_{11}$ structure with a = 4.6874(4) $Å$ and c = 16.8422(12) $Å$ for the Pt-based one (Pd: a = 4.6896 $Å$ and c = 16.891 Å). Specific heat experiments on Ce$_3$PtIn$_{11}$ and Ce$_3$PdIn$_{11}$ have revealed that both compounds undergo two successive magnetic transitions at T$_1$ ~ 2.2 K followed by T$_N$ ~ 2.0 K and T$_1$ ~ 1.7 K and T$_N$ ~ 1.5 K, respectively. Additionally, both compounds exhibit enhanced Sommerfeld coefficients yielding γ$_{Pt}$ = 0.300 J/mol K$^2$ Ce (γ$_{Pd}$ = 0.290 J/mol K$^2$ Ce), hence qualifying them as heavy fermion materials.