Next, the SO-CASPT2 g factors, g ⊥ = 0.72 and g ∥ = 7.77 (see Table ) are also in very good agreement with the experimental values and show a substantial improvement as compared to the SO-CASSCF values (g ⊥ = 0.40, g ∥ = 7.91, respectively) due to the better inclusion of the electron dynamical correlation. The anisotropic orbital and spin contributions to the magnetic moments as a result of the figand field and spin-orbit coupling admixing of the 4f orbitals are also shown. The magnetic moment of the ground KD is significantly anisotropic, as characterized by the prolate m J = ±7/2 state stabilizing the unpaired electron in the bonding active 4f y(3x 2 -y 2 ) and 4f x(x 2 -3y 2 ) orbitals, as shown in Figure . In addition, the EPR hyperfine coupling parameters to the central 171 Yb (I = 1/2) nucleus were calculated from first principle methods using a finite nuclear model. The SO-CASSCF calculations are in good agreement with experiments as shown in Table . Quantitative evaluation of the hyperfine coupling value in the strong relativistic limit requires a forefront level of computational methods and is still in the developing phase. The Fermi contact (A F C ), spin-dipolar (A SD ) and orbital (A orb ) contributions to the hyperfine tensor in Table indicate a dominant anisotropic nuclear spin -electron orbit coupling which leads to the large Yb(III) hyperfine A ⊥ and A ∥ components. The good agreement between calculated and experimental g tensor values and 171 Yb hyperfine couplings indicates that our computational approach, based on DFT-optimized geometry and CAS methods, describes well the electronic structure of Yb(CH(SiMe 3 ) 2 ) 3 . For comparison the first principal calculated molar magnetic susceptibilities of Yb III (CH(SiMe 3 ) 2 ) 3 are provided in Table . The main magnetic axis (χ z ) coincides with the C 3 axis. The calculated isotropic part of the magnetic susceptibility χT at 300 K is 2.30 cm 3 K mol -1