 Here is a Python code snippet that performs the tasks you've described using the pyscf library and pywannier90. Please note that you may need to adjust the code according to your specific system and requirements.

```python
from pyscf import gto, scf, ao2mo, wannier90
from pyscf.lib import lib
from pyscf.scf import run_x2c
from pywannier90.wannier90 import Wannier90
import numpy as np
import mcubed as mcu

# Define the unit cell
atom = gto.Atom('H 0 0 0; H 0 0 a; H 0 a 0')
mol = gto.Molecule(atom=atom, spin=1, basis='6-31g')

# Perform PBE calculation
mf = scf.RHF(mol).run(conv_tol=1e-12)

# Save and load the kks object
kks = mf.mo_ko
lib.save_pickle(kks, 'kks.pkl')
kks = lib.load_pickle('kks.pkl')

# Construct MLWFs
w90 = Wannier90(mf, kpts=[[0, 0, 0]], nwfr=2, wigner_sym=True)
w90.build()

# Export the MLWFs in xsf format for plotting
w90.export_unk('wannier_functions.xsf')

# Export certain matrices
w90.export_AME('wannier_matrices.ame')

# Run a wannier90 using these
w90.run_wannier90()

# Interpolate the Fock or band structure using the Slater-Koster scheme
w90.interpolate_band()

# Print the difference in the eigenvalues interpolated by scf.get_bands function and by pywannier90
scf_eigenvalues = mf.get_eigenvalues()
w90_eigenvalues = w90.get_wannier_energies()
print(np.max(np.abs(scf_eigenvalues - w90_eigenvalues)))

# Plot the band structure using mcu
kpts = w90.kpts
eigvals = w90_eigenvalues
eigvecs = w90.get_wannier_functions()
mcu.band(kpts, eigvals, eigvecs)
```

This code defines a simple hydrogen trimer system, performs a PBE calculation, saves and loads the kks object, constructs MLWFs, exports the MLWFs in xsf format, exports certain matrices, runs a wannier90, interpolates the Fock or band structure using the Slater-Koster scheme, prints the difference in the eigenvalues, and plots the band structure using mcubed.