Synthesis and characterization of the heavy-fermion compound CePtAl₄Ge₂

We report the synthesis of the Ce-based quaternary compound CePtAl₄Ge₂ that crystallizes in the trigonal structure (space group R3¯m, 166) with unit cell parameters, a = 4.1995(5) Å c = 31.851(7) Å and γ = 120°. Powder X-ray diffraction and energy dispersive X-ray spectroscopy show that CePtAl₄Ge₂ (LaPtAl₄Ge₂) is in a single, homogeneous phase. Magnetic susceptibility, electrical resistivity, and heat capacity measurements of CePtAl₄Ge₂ show that it exhibits antiferromagnetic behavior below 2.3 K. The magnetic susceptibility for the magnetic field applied perpendicular (χ_ab) and parallel (χ_c) to the crystalline c-axis is very anisotropic, and the susceptibility ratio (χ_ab/χ_c) reaches a maximum value of 10, indicating that the spin easy axis is within the Ce plane. The entropy recovered at T_N is consistent with the doublet ground state of the crystal field split J = 5/2 multiplet of Ce³⁺ ions.