Strategic Crystal Growth and Physical Properties of Single-Crystalline LnCo₂Al₈ (Ln = La–Nd, Sm, Yb)

Single crystals of LnCo2Al8 (Ln = La–Nd, Sm, Yb) were grown via the metal-flux growth technique and characterized by single crystal X-ray diffraction. LnCo2Al8 adopts the CaCo2Al8-structure type with space group Pbam and unit cell dimensions of a ≈ 12.4 Å, b ≈ 14.4 Å, and c ≈ 4.0 Å. The unit cell volume of LnCo2Al8 (Ln = La–Nd, Sm, Yb) systematically decreases as a function of rare earth, consistent with the lanthanide contraction, except for YbCo2Al8, indicating a divalent Yb2+ state. LnCo2Al8 (Ln = Ce, Pr, Nd) show high temperature Curie–Weiss paramagnetism, and LnCo2Al8 (Ln = Pr, Nd) orders magnetically at TN = 5.6 and 8.7 K, with a fluctuating moment consistent with the trivalent oxidation state of the lanthanides. LnCo2Al8 (Ln = La–Nd, Sm, Yb) are metallic, with CeCo2Al8 having a residual resistivity ratio (RRR) of 20. We present the crystal growth, structural, magnetic, and electrical properties of single crystalline LnCo2Al8 (Ln = La–Nd, Sm, Yb).