Novel graphite biintercalation compound with layers of SmCl3 and ErCl3 is synthetized by the one-zone vapour method. A well defined stage-3 SmCl3 graphite intercalation compound with the c-axis repeat distance I-c = 16.60 +/- 0.07 Angstrom is used as the host matrix. The X-ray diffraction shows a creation of a new compound with I-c = 19.70 +/- 0.058 Angstrom. Based on these data a ...G-SmCl3-G-ErCl3... stacking sequence is proposed. The electron diffraction shows a-axis of the intercalated layer is rotated with respect to the graphene a-axis by 42 degrees, and 19 degrees, 42 degrees for SmCl3 and ErCl3 layers, respectively. The parameters of the lattices obtained are a(SmCl3) = 7.37 Angstrom, a(ErCl3) = 6.75 Angstrom, and b(ErCl3) = 11.73 Angstrom.