The crystal electric field (CEF) plays an essential role in defining the magnetic properties of 4⁢𝑓 materials. It forces the charge density of 4⁢𝑓 electrons and the related magnetic moment to be oriented along a certain direction in the crystal. The CEF and related magnetic properties were widely studied in the past with focus on bulk of 4⁢𝑓 materials, while their surfaces have not received much attention. By the example of the antiferromagnetic material TbRh2⁢Si2 and using first-principles calculations and classical 4⁢𝑓 angle-resolved photoemission (PE) measurements, we show how the CEF and related magnetic properties, linked with the orientation of 4⁢𝑓 moments, are modified at the surface region. Precisely, we studied the CEF characteristics in individual Tb layers for Tb- and Si-terminated surfaces of TbRh2⁢Si2. We show how strongly the CEF changes near the surface and how dramatically it influences the orientation of the 4⁢𝑓 moments relative to the bulk. The instructive message of our study is that a rather valuable information about the CEF-related phenomena can be derived from the temperature dependence of 4⁢𝑓 PE spectra. The presented methodology including the theoretical approach can be further applied to many other layered and quasi-2D rare-earth-based materials for unveiling their surface magnetic properties.