How to read assets folder via route partially generated with a for-loop?

Hi buddies:

This is the project structure (same for all second level folders):

186608-captura-de-pantalla-2021-09-23-182727.png

This is the code:

public class Checker : MonoBehaviour
{
    public Terrain terrain;
    List<Material> grounds = new List<Material>();
    public float maxTime = 5.0f;
    public float currentTime;
    

    // Start is called before the first frame update
    void Start()
    {
        terrain = this.gameObject.GetComponent<Terrain>();

        for (int i = 0; i < 10; i++)
        {

            grounds.Add(Resources.Load<Material>("Materials/Ground" + i + "/Suelo" + i));
        }
    }

    // Update is called once per frame
    void Update()
    {
        if (currentTime >= maxTime)
        {
            currentTime = 0;
            for (int i = 0; i < grounds.Count; i++)
            {
                terrain.materialTemplate = grounds*;*

}
}
else
{
currentTime += Time.deltaTime;
}
}
}
So far this is the result:
Screenshot - 5eece4bdd776cb6f1e5ca9d52797c122 - Gyazo
I’m sure I’m not filling the array properly by either not getting anything as the route may be incorrect, or maybe the “Ground” + i for the route doesn’t work. Either way, I’m at an impass, and would very much appreciate a little push from you buds.
Thanks a lot in advance.

If you want to load a material using

Resources.Load<Material>

that material must be in a folder called Resources. The directory tree would be

Assets/Resources/Materials/Suelo0.mat

Check how Resources folder work here: