You have to either code the symbols as character constants or else code the unicode to create the symbols.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1677706/image.png)
C = [Tag + "_" + List, "k∞", "σ(k∞)", "β", "σ(β)"];
or
C = [Tag + "_" + List, "k"+char(0x221e), char(0x3c3)+"("+char(0x221e)+")", char(0x3b2), char(0x3c3)+"("+char(0x3b2)+")"]