mix two dataframes with every second row

I have two dataframes that I want to mix togther first two of the second table go to the every second two of, so like this:

First table              Second table
column_1                 column_1
1                        5
2                        6
3                        7
4                        8

And then the new table will be like this:

new table
column_1
1
2
5
6
3
4
7
8

Is there easy way to do this with pandas?

I manage to make it like this:

def create_order(length, phase):
    first_list = [i for i in range(length)]
    second_list = [i for i in range(length, length * 2)]
    start_i = 0
    out_list = []
    for i in range(phase, length + 1, phase):
        out_list.extend(first_list[start_i:i])
        out_list.extend(second_list[start_i:i])
        start_i = i
    return out_list

df1 = pd.DataFrame({'col': [1,2,3,4]})
df2 = pd.DataFrame({'col': [5,6,7,8]})
order = create_order(len(df1), 2)
out = pd.concat([df1, df2]).iloc[order]