Hi,
To define anisotropic thermal conductivity for a solid material, select anisotropic for Thermal Conductivity in the Create/Edit material dialog box.
For more details, please refer to user's guide: 8.5. Thermal Conductivity (ansys.com)
If you are not able to access the link, please refer to this forum discussion: Using Help with links (ansys.com)
Hope you find this useful.
Thank you