Anisotroptic Thermal Conductivity Tensor with in-plane and perpendicular-to-plane components

Hello,

I am trying to utilize an anisotropic material, the thermal conductivity for which has been defined in literature as in-plane and perpendicular-to-plane components. How can I utilize these components to define the anisotropic thermal conductivity tensor completely in COMSOL 5.4?

I have been performing my simulations in an 2D-Axissymmetric domain and have been defining a diagonal matrix with components 11, 22 as in-plane and 33 as perpendicular to plane. I am vary of the results since intuitively speaking the other components cannot be zero.

Thanks, Rahul