Study the influence of adjunction of a dielectric or metallic interlayer on the Thermal Boundary Conductance (TBC) measurable between a metallic layer and a diamond substrate. An interlayer does not need to be thick to have a substantial influence influence on the measured TBC. Surface termination with oxygen yields the same TBC contribution as when an Al2O3 layer of finite thickness is used. A metallic interlayer using nickel as thin as 1.5 nm yields the TBC values close to that of the Ni/C system