How can I obtain the variability of different values of a categorical variable by separating into strata?

Hello, I am replicating the results of a study using the following linear mixed-effects model:

The code is:

lme = fitlme(Tabla_datos, 'logxi ~ logH  + Material + Material:logH + (1|key)', ...
             'FitMethod', 'REML');

With this code, I was able to obtain the data for all fixed effects in the following table (highlighted in blue).

However, I still haven’t been able to achieve the results for variability by material (values highlighted in yellow in the table). I understand that MATLAB assumes a common sigma for all random effects, which is why I want to calculate this variability for the different categories (in this case: materials), treating each material as an independent stratum with its own variability.

Thank you in advance for your responses.