In dilute solution, semicrystalline diblock copolymers with one crystallizable block form thin platelet structures consisting of chain-folded crystalline domain between solvated layers of the amorphous block chains. The amorphous block is attached to the crystalline fold surface, forming a model system of tethered chains at a flat interface. We use self-consistent mean field (SCF) theory and a chain-folding model to calculate both the equilibrium platelet thickness and the tethered chain density profile. The theoretical predictions are compared with small-angle X-ray (SAXS) and neutron (SANS) scattering measurements from poly(ethylene oxide)-polystyrene (PEO/PS) suspended in cyclopentane and polyethylene-poly(ethylpropylene) (PE/PEP) suspended in n-decane. The SCF calculations for the crystalline domain thickness are consistent with measured values for diblocks with short crystalline blocks or diblocks having strong enthalpic interactions between the two blocks. The SANS intensity from the tethered chain structure of a PE/PEP diblock is consistent with both SCF calculations and SAXS measurements.