draw circle in xz-plane - matplotlib

Question

I want to draw a circle in the XZ plane. The middlepoint of the circle should be coincide with the green spot.
Unfortunately i can´t find a way to draw the circle in the XZ-Plane (only in XY-plane). The center of the circle is (0,0).
Do you have an idea to draw the circle in the XZ-Plane?
That´s the code:
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
def singular_value_decomposition(X):
import numpy as np
C = np.average(X,axis=0)
print(C)
CX = X-C
U,S,V = np.linalg.svd(CX)
return C,V
def cloud():
import numpy as np
h = 0.5*(1+np.sqrt(5))
p1 = np.array([[0,1,h],[0,1,-h],[0,-1,-h]])
p2 = p1[:,[1,2,0]]
p3 = p1[:,[0,1,2]]
return np.vstack((p1,p2,p3))
A = cloud()
print(A)
centroid, V = singular_value_decomposition(A)
# calculate a circle
theta = np.linspace(0, 2*np.pi, 100)
r = np.sqrt(0.5)
x1 = r*np.cos(theta)
x2 = r*np.sin(theta)
# plot graph
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.scatter(centroid[0], centroid[1], centroid[2], color='green',s=100)
#draw circle
ax.plot(x1,x2)
ax.set_xlabel('$X$',fontsize=20)
ax.set_ylabel('$Y$',fontsize=20)
ax.set_zlabel('$Z$', fontsize=20)
plt.show()